KR20230041762A - Cover member, base film for cover member, and display device provided with them - Google Patents

Abstract

In addition to improving the handleability of the cover member, an object of the present invention is a cover member and a base film for a cover member that do not crease in the base film included in the cover member when repeatedly bent, and a display provided therewith. to provide the device. The cover member of the present invention is a cover member having a base film of 1 μm or more and less than 15 μm and a transparent substrate of 5 μm or more and less than 50 μm, and connecting the origin and break point in a stress-strain curve of the base film Characterized in that the slope of the straight line is 1.1 or more and 25.0 or less.

Description

Cover member, base film for cover member, and display device provided with them

The present invention relates to a cover member, a base film for a cover member, and a display device provided with them. More specifically, the present invention relates to a cover member, a base film for a cover member, and a display device provided with the cover member, which, in addition to improving handleability of the cover member, does not cause creases in the base film included in the cover member.

Recently, many developments of foldable or rollable flexible displays have been carried out. The display is constituted by a display unit including a cover glass unit for the purpose of protecting the display (hereinafter, also referred to as a "cover member" in the present invention) and a polarizing plate.

Here, since flexibility is required when a glass substrate is used as the transparent substrate used in the cover glass unit, for example, thinning of the glass substrate itself is required. In response to these requests, production of thin glass is required. A method and the like are disclosed (see, for example, Patent Literature 1).

On the other hand, when laminating a polymer layer (protective film) on a glass substrate for the purpose of protecting the glass substrate, an invention of controlling waviness on the surface of the polymer layer is disclosed (see, for example, Patent Document 2. ).

In the flexible display having the folding specification, each member is thinned, so that the bending radius of the cover member becomes smaller when the display is folded. In that case, according to the study of the present inventors, the protective film provided on the cover member (also referred to as "substrate film" in the present invention) has a protective function to the extent that cracks do not occur in the glass base material when the cover member is folded. It has been found that, in addition to improvement in (press-fit strength), a property that no crease is formed in the protective film when the cover member is repeatedly bent is required.

However, in a cover member composed of a laminate of a glass substrate and a protective film manufactured by the technical means disclosed above, the protective function is improved when it is made thinner, and folds on the protective film when repeatedly bent. It was difficult to achieve compatibility of characteristics that did not occur.

International Publication No. 2017/066924 Japanese Patent Publication No. 2002-534305

The present invention has been made in view of the above problems and circumstances, and the problem to be solved is, in addition to improving the handleability of the cover member, a cover member and a cover that do not crease in the base film provided with the cover member when repeatedly bent. It is providing the base film for members, and the display apparatus provided with them.

In order to solve the above problems, in the process of examining the causes of the above problems, the present inventors have a base film and a transparent base material having a specific thickness, and the relationship between the stress of the base film and its deformation. In this study, it was found that when a specific relationship is satisfied, a cover member having a characteristic that, in addition to improving the handleability of the cover member, no creases are formed on the base film with which the cover member is provided, can be obtained.

That is, the above subject concerning the present invention is solved by the following means.

1. A cover member having a substrate film of 1 μm or more and less than 15 μm and a transparent substrate of 5 μm or more and less than 50 μm,

A cover member characterized in that the slope of a straight line connecting the origin and the break point in the stress-strain curve of the base film is 1.1 or more and 25.0 or less.

2. When the bonding surface of the base film with the transparent substrate is the A surface and the back surface of the base film relative to the A surface is the B surface,

The cover member according to claim 1, wherein the film density (ρ _A ) of the surface A is smaller than the film density (ρ _B ) of the surface B.

3. When the bonded surface of the base film with the transparent substrate is the A surface, and the back surface of the base film relative to the A surface is the B surface,

Claim 1 or 2, characterized in that the value of the ratio (ρ _A /ρ _B ) of the film density (ρ _B ) of the B surface to the film density (ρ _A ) of the A surface is within the range of 0.80 to 0.95. The cover member according to claim.

4. The cover member according to any one of 1 to 3, wherein the base film contains rubber particles within a range of 40 to 85% by mass.

5. The elastic modulus of the transparent substrate is in the range of 55 to 80 GPa, and the ratio of the elastic modulus of the transparent substrate to the elastic modulus of the base film (elastic modulus of the transparent substrate / elastic modulus of the base film) is 30 or more, characterized in that The cover member according to any one of claims 1 to 4.

6. As a base film for cover members,

The base film is 1 μm or more and less than 15 μm,

A base film for a cover member, characterized in that the slope of a straight line connecting the origin and the break point in the stress-strain curve of the base film is 1.1 or more and 25.0 or less.

7. The base film is bonded to a transparent base,

When the bonding surface of the base film with the transparent substrate is the A surface and the back surface of the base film relative to the A surface is the B surface,

The base film for a cover member according to claim 6, wherein the film density (ρ _A ) of the surface A is smaller than the film density (ρ _B ) of the surface B.

8. The base film is bonded to a transparent base,

When the bonding surface of the base film with the transparent substrate is the A surface and the back surface of the base film relative to the A surface is the B surface,

Claim 6 or 7, characterized in that the ratio of the film density (ρ _B ) of the B surface to the film density (ρ _A ) of the A surface (ρ _A /ρ _B ) is in the range of 0.80 to 0.95. The base film for a cover member according to the item.

9. The base film for a cover member according to any one of 6 to 8, characterized in that the base film contains rubber particles within a range of 40 to 85% by mass.

10. A display device comprising the cover member according to any one of items 1 to 5 or the base film for a cover member according to any one of items 6 to 9.

In addition to improving the handleability of the cover member by the means of the present invention, a cover member and a base film for a cover member that do not crease in the base film provided to the cover member when repeatedly bent, and a base film for the cover member, and providing them A display device may be provided.

Although the expression mechanism or action mechanism of the effect of this invention is not clear, it guesses as follows.

The cover member of the present invention is composed of a laminate of a base film having a specific thickness range and a transparent base material, and the slope of a straight line connecting the origin and the break point in a stress-strain curve of the base film is 1.1 or more and 25.0 or less. that is characterized by

In addition to improving the handleability of the cover member due to these features, a cover member that does not crease in the base film with which the cover member is provided when repeatedly bent can be obtained.

Here, "handling of the cover member" means, in the present invention, that during the opening and closing operation by folding the cover member, the base film provided to the cover member exhibits a protective function (press-fit strength), and cracks, etc. means that it does not cause In addition, "fold" means that the base film is whitened at the folded portion with opening and closing operations by repeated folding, and in addition to being observed as a crease, the base film is peeled off from the transparent base material, resulting in image deformation, etc. It means deterioration of visibility.

When the slope of the straight line connecting the origin and the breaking point in the stress-strain curve of the base film exceeds 25.0, that is, when the base film is hard and the breaking point is reached quickly, the base film is elongated. In the closed state, that is, when the device is closed, since a rapid increase in stress occurs especially on the outside of the base film, in repeated opening and closing operations, a difference in physical property deterioration occurs between the outside and the inside, and the folded part Whitening or poor adhesion occurs, and the above-mentioned "fold marks" are visually recognized. In addition, since stress is concentrated directly on the transparent substrate at the time of press-fitting of the transparent substrate, it is estimated that cracking of the transparent substrate is likely to occur.

On the other hand, when the slope of the straight line is less than 1.1 and the base film is soft, in the repeatedly performed opening and closing operation, the difference in physical property deterioration between the outside and the inside hardly occurs, but accompanying the opening and closing operation, the base film Since the entire base film repeats expansion and contraction in a form that is integrally followed by this transparent base material, the base film floats due to adhesion failure or the like in the folded portion, reducing visibility. In addition, since the base film is too soft when the base film is press-fitted together with the transparent base material, it is estimated that the amount of physical deformation of the transparent base material is too large and cracking of the transparent base material is likely to occur.

1A is a cross-sectional view of a laminate of a base film and a transparent base material.
1B is a cross-sectional view of a laminate of a base film and a transparent base in another embodiment.
1C is a schematic diagram when the laminate is folded
Fig. 1D is a schematic view when a laminate of another aspect is folded.
2 is a graph showing the slope of a straight line connecting a stress-strain curve of a base film and an origin and a break point;
Fig. 3 is a schematic diagram showing a method for manufacturing a base film according to an embodiment of the present invention;
4 is a schematic diagram showing an example of a method for manufacturing a glass substrate applied to a transparent substrate.
Fig. 5A is a schematic view showing bonding of a base film with a support and a transparent base.
Fig. 5B is a schematic view showing bonding of a base film with a support in another embodiment and a transparent base material;
6 shows an application example of a cover member to an organic EL display, which is an example of a display device of the present invention.

A cover member of the present invention is a cover member having a base film having a thickness of 1 μm or more and less than 15 μm, and a transparent substrate having a thickness of 5 μm or more and less than 50 μm, wherein the origin and break point in a stress-strain curve of the base film It is characterized in that the slope of the straight line connecting is 1.1 or more and 25.0 or less. This feature is a technical feature common to or corresponding to the following embodiments.

In an embodiment of the present invention, from the viewpoint of the effect expression of the present invention, when the bonding surface of the base film with the transparent substrate is surface A, and the back surface of the base film relative to surface A is surface B, It is preferable that the film density (ρ _A ) of the surface A is smaller than the film density (ρ _B ) of the surface B, and the film density (ρ B ) of the surface B relative to the film density (ρ _A ) of the surface _A It is preferable that the value of the ratio (ρ _A /ρ _B ) is in the range of 0.80 to 0.95. This is due to the fact that when the cover member is folded to the transparent substrate side, the B surface side of the base film is subjected to more tensile stress than the A surface side, but the tensile stress can be relieved if the film density on the A surface side is low. .

Moreover, it is preferable that the said base film contains a rubber particle within the range of 40-85 mass %. The effect of improving impact resistance by adding a large amount of rubber particles leads to improvement in crease resistance when subjected to repeated bending.

The elastic modulus of the transparent substrate is in the range of 55 to 80 GPa, and the ratio of the elastic modulus of the transparent substrate to the elastic modulus of the base film (elastic modulus of the transparent substrate/elastic modulus of the base film) is preferably 30 or more. This is to use a base film having a lower elastic modulus, that is, to use a base film having a lower elastic modulus, that is, to provide a cover member that does not cause improvement in press-fit strength or crease by using a transparent base material having a low elastic modulus due to thinning. It depends on being able to further improve the protective function of a transparent base material by making the value of (elastic modulus of a transparent base material/elastic modulus of a base film) into 30 or more.

Further, the base film for a cover member of the present invention has a thickness (also referred to as “film thickness”) within a range of 1 μm or more and less than 15 μm, and the origin and break point in the stress-strain curve of the base film It is characterized in that the slope of the straight line connecting is 1.1 or more and 25.0 or less. By adjusting the inclination of the straight line within the above range, the press-fit strength and crease resistance of the base film are improved, and the handleability when the base film is attached to the cover member is improved.

In the base film, when the bonding surface of the base film with the transparent substrate is the A surface and the back surface of the base film relative to the A surface is the B surface, the film density (ρ _A ) of the A surface is It is preferably smaller than the film density (ρ _B ) of surface B, and the value of the ratio (ρ _A /ρ _B ) of the film density (ρ _B ) of surface B to the film density (ρ _A ) of surface A is 0.80. What is within the range of -0.95 is more preferable from a viewpoint of the above-mentioned effect.

Moreover, it is similarly preferable that the said base film contains a rubber particle within the range of 40-85 mass %.

The display device of the present invention is characterized by comprising the cover member of the present invention or the base film for the cover member of the present invention. With the display device, in addition to improving the handleability of the cover member, a display device provided with a foldable display or a rollable display that does not crease in the base film provided with the cover member when repeatedly bent can be obtained. there is.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a detailed description will be given of the form and aspect for implementing the present invention, its components, and the present invention. In addition, in this application, "-" is used by the meaning which includes the numerical value described before and after that as a lower limit value and an upper limit value.

<<Overview of Cover Member of the Present Invention>>

A cover member of the present invention is a cover member having a base film having a thickness of 1 μm or more and less than 15 μm, and a transparent substrate having a thickness of 5 μm or more and less than 50 μm, wherein the origin and break point in a stress-strain curve of the base film It is characterized in that the slope of the straight line connecting is 1.1 or more and 25.0 or less.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view of a laminate of a base film and a transparent substrate in a cover member of the present invention, and a schematic view when the cover member (laminate) is folded.

1A shows the minimum configuration of the cover member 10 of the present invention, and the base film 1 is bonded to the transparent base material 3 via the pressure-sensitive adhesive layer 4 to form a laminate. When the base film 1 is bonded to the transparent base material 3, the bonding surface of the base film 1 to the transparent base material 3 is surface A, and the back surface of the base film to the surface A is B make it cotton

1B shows another aspect of the cover member 10 of the present invention. The base film 1 is bonded to the transparent base material 3 through the pressure-sensitive adhesive layer 4, and the base film 2 is bonded to the transparent base material 3 through the pressure-sensitive adhesive layer 4 to form a laminate. It indicates the shape of the formation. The base film 2 may be a film having the same specifications as the base film 1, or may be a film having different materials and specifications. For example, in order to improve surface hardness, functional films, such as a hard coat film, may be sufficient.

FIG. 1C is a schematic view when the cover member 10 shown in FIG. 1A is folded to the transparent substrate 3 side. Here, the bending radius when folded means the inner radius R of the folded portion when the cover member 10 is folded in FIG. 1C or 1D.

As described above, when the cover member is folded to the transparent substrate 3 side, the B surface side of the base film is subjected to a higher tensile stress than the A surface side, but if the film density on the A surface side is low, the tensile stress is relieved can make it

FIG. 1D is a schematic view when the cover member 10 shown in FIG. 1B is folded to the transparent substrate 3 side. Also in this case, the B surface side of the base film 1 is subjected to more tensile stress than the A surface side, but the tensile stress can be relieved if the film density on the A surface side is low.

The stress-strain curve according to the present invention shows the relationship between tensile stress and tensile breaking elongation of a base film, which is measured based on JIS K7127:1999.

The base film is cut out to a size of 100 mm (MD direction: longitudinal direction) x 10 mm (TD direction: transverse direction) to obtain a sample film. This sample film was subjected to humidity control for 24 hours in an environment of 23 ° C. 55% RH, and the sample film after humidity control was prepared in accordance with JIS K7127: 1999 using Tensilon RTC-1225A manufactured by Orientec, The distance between chucks is set to 50 mm, and a stress-strain curve until fracture is obtained while pulling in the MD direction. In the stress-strain curve, the vertical axis represents stress (MPa), and the horizontal axis represents tensile elongation at break (%). The measurement of the stress-strain curve is performed under the conditions of 23°C/55% RH and a tensile speed of 50 mm/min.

A method for determining the inclination of a straight line related to the present invention from the stress-strain curve of the base film obtained by the above measurement will be described with reference to the drawings.

2 is a graph showing the slope of a straight line connecting a stress-strain curve of a base film and an origin and a break point.

The base film is subjected to a tensile test to take a breaking point X after stretching. When a straight line Y connecting the breaking point X and the origin (point 0) is drawn, the slope α of this straight line is referred to as " It is defined as "the slope of a straight line connecting the origin and the break point in the stress-strain curve of the base film." As described above, the inclination α needs to be 1.1 or more and 25.0 or less from the viewpoint of obtaining the effect of the present invention, and is rich in elasticity but not too hard, thereby improving the press-fitting strength of the base film and handling of the cover member. In addition to improving the properties, it is possible to obtain a cover member in which folds do not occur in the base film itself provided in the cover member when subjected to repeated bending.

Hereinafter, the components of the present invention will be described in detail. However, in the following description, the present invention is not limited to this.

[1] Base film

[1.1] Outline of base film

In the following description, the "base film" is described as the "base film 1" in FIG. 1 unless otherwise specified.

The substrate film according to the present invention has a film thickness within the range of 1 μm or more and less than 15 μm, and the slope of a straight line connecting the origin and the break point in the stress-strain curve of the substrate film is 1.1 or more and 25.0 or less. As a feature, in addition to improving handleability such as press-in strength when provided on a cover member, when provided on the cover member, it has an effect of not forming folds in the base film itself when repeatedly bent.

As described above, when the slope of the straight line exceeds 25.0, since a rapid increase in stress occurs especially on the outside of the base film in the state in which the base film is extended, that is, in the state in which the device is closed, repeating the In the opening/closing operation to be performed, a difference in physical property deterioration between the outside and the inside occurs, and the folded portion is whitened or adhesion failure occurs, which is visually recognized as a crease. In addition, since stress is concentrated directly on the transparent substrate during press-fitting of the transparent substrate, cracking of the transparent substrate is likely to occur.

On the other hand, when the slope of the straight line is less than 1.1 and the base film is soft, the entire base film repeats expansion and contraction in a form in which the base film integrally follows the transparent base along with the opening and closing operation, so that the folded portion In this, the base film is lifted due to poor adhesion and the like, and the visibility is lowered, and it is visually recognized as a crease. In addition, since the base film is too soft when the base film is press-fitted together with the transparent base material, the amount of physical deformation of the transparent base material is too large, and cracking of the transparent base material is likely to occur.

Moreover, if the said film thickness is less than 1 micrometer, elasticity as a base film will become weak and the press-in strength of a cover member will fall. Moreover, since elasticity as a base film becomes strong as it is 15 micrometers or more, and the said crease becomes easy to generate|occur|produce with repeated opening and closing of a display, it is necessary that it is within the said range.

In addition, when the bonding surface of the base film with the transparent substrate is A surface and the back surface of the base film relative to the A surface is B surface, the film density (ρ _A ) of the A surface is It is preferably smaller than the film density (ρ _B ), and the value of the ratio (ρ _A /ρ _B ) of the film density (ρ _B ) of the B surface to the film density (ρ _A ) of the A surface is 0.80 to 0.95. It is desirable to be within the range. This is because when the cover member is folded to the transparent substrate side, the B-side of the base film is subjected to more tensile stress than the A-side, but if the film density on the A-side is low, the tensile stress can be relieved.

<Measurement of Density of Surface A and Surface B of Base Film>

The density of the surface (A side and B side) of the base film is measured using the X-ray reflectance method (XRR method). X-rays are totally reflected when they are incident on the film surface at a very shallow angle, and when the angle of the incident X-rays is greater than the critical angle of total reflection, the X-rays penetrate the inside of the film and the reflectance is lowered. The reflectance profile measured by the XRR method can be analyzed using dedicated reflectance analysis software. In the present invention, when θa is the angle at which the reflectance starts to decrease, 2θ is in the range of 2θa to 2θa + 0.1°. , the surface density is the density at which the fitting error between the measurement result and the calculation result is the smallest. At that time, the surface roughness is within the range of 0 nm to 1 nm, and fitting is performed.

A base film is cut out to a size of 30 mm x 30 mm, fixed to a sample stage, and measured under the following measurement conditions.

(Measuring conditions)

·Device : Thin-film X-ray diffractometer (ATX-G manufactured by Rigaku Co., Ltd.)

・Sample size : 30 mm × 30 mm

･Incident X-ray wavelength : 1.5405 Å

・Measurement range (θ) : 0 to 6°

・Analysis software : Reflectance analysis software GXRR (manufactured by Rigaku Co., Ltd.)

In order to set the value of the ratio (ρ _A /ρ _B ) of the film density (ρ _B ) of the surface B to the film density (ρ _A ) of the surface A to be in the range of 0.80 to 0.95, in the manufacturing process of the base film As an example, adjustment can be made using the following knowledge.

(a) Change the amount of rubber particles or microparticles relative to the resin. For example, if the amount of rubber particles or microparticles is increased, the diffusion of the solvent is promoted so that the difference in density between the surface and the back surface is less likely to occur.

(b) The solid content concentration in dope is changed. For example, when the solid content is high, the solvent is relatively small, so that the difference in density does not occur easily.

(c) Change the drying method. For example, in addition to gentle drying, spot drying (exposing a heater to the surface) can increase the difference in density.

By combining means derived from the knowledge of (a) to (c), it is possible to adjust the value of the density ratio (ρ _A /ρ _B ) of the surface A/surface B to within the range of 0.80 to 0.95.

[1.2] Material of base film

The resin used in the base film according to the present invention is not particularly limited, and cellulose ester-based resins, cycloolefin-based resins, fumaric acid diester-based resins, polypropylene-based resins, (meth)acrylic-based resins, polyester-based resins, and polyamides are used. Relate-type resins, polyimide-type resins, and styrene-type resins or composite resins thereof are exemplified. Preferred resins include those containing a linear polymeric material having a carbonyl group in the side chain, or a cyclic structure in the main chain. (meth)acrylic resin, styrene-(meth)acrylate copolymer, cycloolefin resin or polyi from the viewpoint of controlling physical properties such as bending resistance and improving optical properties Mead type resin etc. can be used.

<(meth)acrylic resin>

It is preferable that the (meth)acrylic resin used for the base film contains at least a structural unit (U1) derived from methyl methacrylate and a structural unit (U2) derived from phenylmaleimide. The (meth)acrylic resin containing the structural unit (U2) derived from phenylmaleimide also has the advantage of reducing the photoelastic coefficient of the base film and making nonuniformity less likely to occur even if it expands after moisture absorption.

The (meth)acrylic resin may further contain structural units other than those described above. Examples of such other structural units include (meth)acrylic acid alkyl esters such as adamantyl acrylate; (meth)acrylic acid cycloalkyl esters such as 2-ethylhexyl acrylate; and the like. Among these, it is preferable to further include a structural unit (U3) derived from an alkyl acrylate ester from the viewpoint of reducing deterioration of brittleness by including the structural unit (U2) derived from phenylmaleimide.

That is, the (meth)acrylic resin contains a structural unit (U1) derived from methyl methacrylate, a structural unit (U2) derived from phenylmaleimide, and a structural unit (U3) derived from an alkyl acrylate ester. it is more preferable

The content of the structural unit (U1) derived from methyl methacrylate is preferably in the range of 50 to 95% by mass, and preferably in the range of 70 to 90% by mass, based on all the structural units constituting the (meth)acrylic resin. more preferable

Since the structural unit (U2) derived from phenylmaleimide has a relatively rigid structure, it can improve the mechanical strength of a base film. In addition, since the structural unit (U2) derived from phenylmaleimide has a relatively bulky structure and can have microscopic voids through which rubber particles can move in the resin matrix, the rubber particles can be transported to the surface layer portion of the base film. can be easily ubiquitous in

The content of the structural unit (U2) derived from phenylmaleimide is preferably in the range of 1 to 25% by mass with respect to all the structural units constituting the (meth)acrylic resin. When the content of the structural unit (U2) derived from phenylmaleimide is 1% by mass or more, the preservability of the base film in a high-humidity environment is excellent. If it is 25% by mass or less, the brittleness of the base film is not easily inhibited excessively. The content of the structural unit (U2) derived from phenylmaleimide is more preferably in the range of 7 to 15% by mass from the above viewpoint.

Since the structural unit (U3) derived from an acrylic acid alkyl ester can impart moderate flexibility to resin, brittleness can be improved by including, for example, a structural unit (U2) derived from phenylmaleimide.

The alkyl acrylate ester is preferably an alkyl acrylate ester having 1 to 7 carbon atoms in the alkyl moiety, preferably 1 to 5 carbon atoms. Examples of the alkyl acrylate ester include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate and the like.

The content of the structural unit (U3) derived from an alkyl acrylate ester is preferably in the range of 1 to 25% by mass with respect to all the structural units constituting the (meth)acrylic resin. When the content of the structural unit (U3) derived from an alkyl acrylate ester is 1% by mass or more, appropriate flexibility can be imparted to the (meth)acrylic resin, so that the base film is not too brittle and is not easily broken. When the content of the structural unit (U3) derived from an alkyl acrylate ester is 25% by mass or less, the Tg of the base film does not become too low, and the storage property of the base film in a high humidity environment is excellent. The content of the structural unit (U3) derived from an alkyl acrylate ester is more preferably in the range of 5 to 15% by mass from the above viewpoint.

The ratio of the structural unit (U2) derived from phenylmaleimide to the total amount of the structural unit (U2) derived from phenylmaleimide and the structural unit (U3) derived from alkyl acrylate is in the range of 20 to 70% by mass It is desirable to be When the ratio is 20% by mass or more, the elastic modulus of the base film is easily increased, and when the ratio is 70% by mass or less, the base film does not become too brittle.

It is preferable that it is 100 degreeC or more, and, as for the glass transition temperature (Tg) of (meth)acrylic-type resin, it is more preferable that it is the range of 120-150 degreeC. When the Tg of the (meth)acrylic resin is within the above range, it is easy to increase the heat resistance of the base film. In order to adjust the Tg of the (meth)acrylic resin, it is preferable to adjust the content of the structural unit (U2) derived from phenylmaleimide or the structural unit (U3) derived from an acrylic acid alkyl ester, for example.

The weight average molecular weight (Mw) of the (meth)acrylic resin is not particularly limited and can be adjusted according to the purpose. The weight average molecular weight of the (meth)acrylic resin is, for example, from the viewpoint of promoting entanglement of resin molecules to increase the toughness of the base film so that it does not easily break, and moderately high humidity expansion coefficient. Curl amount suitable for adhesion From the viewpoint of making adjustment easy, it is preferably 100,000 or more, and more preferably 1,000,000 or more. The toughness of the base film obtained can be improved as the weight average molecular weight of (meth)acrylic-type resin is 1 million or more. Accordingly, in the manufacturing process, when conveying as a laminated film described later, breakage of the base film due to conveying tension can be suppressed, and conveying stability can be improved. The weight average molecular weight of the (meth)acrylic resin is more preferably in the range of 1,500,000 to 3,000,000 from the same viewpoint. The measuring method of a weight average molecular weight is as follows.

<Gel permeation chromatography>

Solvent: Methylene chloride

Column: Shodex K806, K805, K803G (three manufactured by Showa Denko Co., Ltd. were connected and used)

Column temperature: 25 ℃

Sample concentration: 0.1% by mass

Detector: RI Model 504 (manufactured by GL Science)

Pump: L6000 (manufactured by Hitachi, Ltd.)

Flow rate: 1.0 mL/min

Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Co., Ltd.) A calibration curve by 13 samples within the range of Mw = 500 to 2800000 was used. It is preferable to use 13 samples at substantially equal intervals.

<Styrene/(meth)acrylate copolymer>

A styrene/(meth)acrylate copolymer (hereinafter also referred to as a styrene/acrylic resin) is excellent in transparency when used for a base film. Moreover, since the hygroscopic expansion coefficient can also be adjusted with the copolymerization ratio of a styrene part, curl as a laminated body can be controlled by changing these ratios.

A styrene acrylic resin is formed by addition polymerization of at least a styrene monomer and a (meth)acrylic acid ester monomer. Styrene monomers include styrene derivatives having known side chains or functional groups in the styrene structure in addition to styrene represented by the structural formula of CH ₂ =CH-C ₆ H ₅ .

The (meth)acrylic acid ester monomer is an acrylic acid ester or methacrylic acid ester represented by CH(R ₁ )=CHCOOR ₂ (R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents an alkyl group having 1 to 24 carbon atoms.) In addition to acid esters, acrylic acid ester derivatives and methacrylic acid ester derivatives having known side chains or functional groups in the structure of these esters are included.

Examples of the styrene monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butyl styrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene and p-n-dodecylstyrene.

Examples of the (meth)acrylic acid ester monomer include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl Acrylic acid ester monomers, such as acrylate (2EHA), stearyl acrylate, lauryl acrylate, and phenyl acrylate; Methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate Methacrylic acid esters, such as stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethyl amino ethyl methacrylate, and dimethyl amino ethyl methacrylate; is included

In addition, in this specification, a "(meth)acrylic acid ester monomer" is a general term of a "acrylic acid ester monomer" and a "methacrylic acid ester monomer", and means one or both of them. For example, "methyl (meth)acrylate" means either or both of "methyl acrylate" and "methyl methacrylate."

One kind or more may be sufficient as the said (meth)acrylic acid ester monomer. For example, to form a copolymer using a styrene monomer and two or more types of acrylic acid ester monomers, to form a copolymer using a styrene monomer and two or more types of methacrylic acid ester monomers, and to form a copolymer using a styrene monomer and acrylic acid ester It is possible to form a copolymer by using a monomer and a methacrylic acid ester monomer in combination.

It is preferable that it is the range of 5000-150000, and, as for the weight average molecular weight (Mw) of the said styrene acrylic resin, it is more preferable that it is the range of 30000-120000 from a viewpoint of easy control of plasticity.

The styrene acrylic resin used for this invention may be a commercial item, and MS resin "TX320XL" by Denka Corporation is mentioned as an example.

<Rubber Particles>

In the case of using a (meth)acrylic resin or a styrene-(meth)acrylate copolymer, the base film according to the present invention contains rubber particles within a range of 40 to 85% by mass to improve toughness (flexibility) It is preferable from the viewpoint of imparting and improving crease resistance.

Rubber particles are particles containing a rubbery polymer. The rubbery polymer is a soft crosslinked polymer having a glass transition temperature of 20°C or less. Examples of such crosslinked polymers include butadiene-based crosslinked polymers, (meth)acrylic-based crosslinked polymers, and organosiloxane-based crosslinked polymers. Among them, (meth)acrylic crosslinked polymers are preferred, and acrylic crosslinked polymers (acrylic rubber-like polymers) are more preferred from the viewpoint that the refractive index difference with (meth)acrylic resin is small and the transparency of the base film is not easily impaired.

That is, the rubber particles are preferably particles containing the acrylic rubber-like polymer (a).

Regarding the acrylic rubbery polymer (a):

The acrylic rubber-like polymer (a) is a crosslinked polymer containing as a main component a structural unit derived from an acrylic acid ester. "Contained as a main component" means that the content of the structural unit derived from acrylic acid ester falls within the range described below. The acrylic rubber-like polymer (a) is a multitube having a structural unit derived from an acrylic acid ester, a structural unit derived from another monomer copolymerizable therewith, and two or more radically polymerizable groups (non-conjugated reactive double bonds) in one molecule. It is preferable that it is a crosslinked polymer containing a structural unit derived from a functional monomer.

Acrylic acid ester is an alkyl group such as methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, benzyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, and n-octyl acrylate. It is preferable that it is a C1-C12 acrylic acid alkylester. One type may be sufficient as acrylic acid ester, and two or more types may be sufficient as it.

The content of the structural unit derived from the acrylic acid ester is preferably in the range of 40 to 80% by mass, and more preferably in the range of 50 to 80% by mass, based on all the structural units constituting the acrylic rubber-like polymer (a1). . When the content of the acrylic acid ester is within the above range, it is easy to impart sufficient toughness to the protective film.

Other monomers which can be copolymerized are those other than polyfunctional monomers among the monomers which can be copolymerized with acrylic acid ester. That is, the monomer which can be copolymerized does not have two or more radically polymerizable groups. For the example of the monomer which can be copolymerized, Methacrylic acid ester, such as methyl methacrylate; Styrene, such as styrene and methyl styrene; (meth)acrylonitriles; (meth)acrylamides; (meth)acrylic acid is included. Especially, it is preferable that the other monomer which can be copolymerized contains styrene. One type or two or more types may be sufficient as the other monomer which can be copolymerized.

The content of structural units derived from other copolymerizable monomers is preferably in the range of 5 to 55% by mass, and more preferably in the range of 10 to 45% by mass, based on all the structural units constituting the acrylic rubber-like polymer (a). desirable.

Examples of the polyfunctional monomer include allyl (meth) acrylate, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl maleate, divinyl adipate, divinylbenzene, ethylene glycol di(meth) ) Acrylate, diethylene glycol (meth) acrylate, triethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, dipropylene glycol di ( meth)acrylate and polyethylene glycol di(meth)acrylate are included.

The content of structural units derived from polyfunctional monomers is preferably in the range of 0.05 to 10% by mass, and more preferably in the range of 0.1 to 5% by mass, based on all the structural units constituting the acrylic rubber-like polymer (a). do. When the content of the polyfunctional monomer is 0.05% by mass or more, the degree of crosslinking of the obtained acrylic rubber-like polymer (a) is easily increased, so that the hardness and rigidity of the obtained base film are not excessively impaired, and when the content is 10% by mass or less, the toughness of the base film This does not interfere well.

The monomer composition constituting the acrylic rubber-like polymer (a) can be measured, for example, by a peak area ratio detected by thermal decomposition GC-MS.

It is preferable that it is 0 degreeC or less, and, as for the glass transition temperature (Tg) of a rubbery polymer, it is more preferable that it is -10 degreeC or less. When the glass transition temperature (Tg) of the rubbery polymer is 0°C or lower, appropriate toughness can be imparted to the film. The glass transition temperature (Tg) of the rubbery polymer is measured in the same manner as described above.

The glass transition temperature (Tg) of the rubbery polymer can be adjusted by the composition of the rubbery polymer. For example, in order to lower the glass transition temperature (Tg) of the acrylic rubber-like polymer (a), it is necessary to increase the mass ratio of acrylic acid ester having 4 or more carbon atoms in the alkyl group/other copolymerizable monomers in the acrylic rubber-like polymer (a). (For example, it is 3 or more, Preferably it is the range of 4-10.) It is preferable.

The particles containing the acrylic rubber-like polymer (a) are arranged around a hard layer made of the particles made of the acrylic rubber-like polymer (a) or a hard cross-linked polymer (c) having a glass transition temperature of 20°C or higher. particles having a soft layer made of the acrylic rubber-like polymer (a) (these are also referred to as "elastomers") may be used; It may be a particle composed of an acrylic graft copolymer obtained by polymerizing a mixture of monomers such as methacrylic acid ester in at least one stage in the presence of the acrylic rubber-like polymer (a). The particle made of the acrylic graft copolymer may be a core cell type particle having a core portion containing the acrylic rubber-like polymer (a) and a cell portion covering the core portion.

Regarding the core-shell type rubber particles containing the acrylic rubber-like polymer:

(core part)

The core part contains the acrylic rubber-like polymer (a) and may further contain a hard crosslinked polymer (c) as needed. That is, the core portion may have a soft layer made of an acrylic rubber-like polymer and a hard layer made of a hard crosslinked polymer (c) arranged on the inner side thereof.

The crosslinked polymer (c) may be a crosslinked polymer containing methacrylic acid ester as a main component. That is, it is preferable that the crosslinked polymer (c) is a crosslinked polymer containing a structural unit derived from an alkyl methacrylate ester, a structural unit derived from another monomer copolymerizable therewith, and a structural unit derived from a polyfunctional monomer. do.

The methacrylic acid alkyl ester may be the methacrylic acid alkyl ester described above; Other copolymerizable monomers may be the above-described styrenes, acrylic acid esters, and the like; Examples of the polyfunctional monomer include the same ones as those exemplified as the above-mentioned polyfunctional monomer.

The content of the structural unit derived from the alkyl methacrylate ester may be in the range of 40 to 100% by mass with respect to all the structural units constituting the crosslinked polymer (c). The content of structural units derived from other copolymerizable monomers may be in the range of 60 to 0% by mass with respect to all the structural units constituting the other crosslinked polymer (c). The content of the structural unit derived from the polyfunctional monomer may be in the range of 0.01 to 10% by mass with respect to all the structural units constituting the other crosslinked polymer.

(cell part)

The cell portion contains a methacrylic polymer (b) (another polymer) containing as a main component a structural unit derived from a methacrylic acid ester grafted to the acrylic rubbery polymer (a). "Contained as a main component" means that the content of the structural unit derived from methacrylic acid ester falls within the range described below.

It is preferable that the methacrylic acid ester which comprises a methacrylic polymer (b) is a C1-C12 methacrylic acid alkyl ester of an alkyl group, such as methyl methacrylate. One type may be sufficient as methacrylic acid ester, and two or more types may be sufficient as it.

It is preferable that content of methacrylic acid ester is 50 mass % or more with respect to all the structural units which comprise a methacrylic polymer (b). When the content of the methacrylic acid ester is 50% by mass or more, compatibility with a methacrylic resin containing a structural unit derived from methyl methacrylate as a main component is easily obtained. As for content of methacrylic acid ester, it is more preferable that it is 70 mass % or more with respect to all the structural units which comprise a methacrylic polymer (b) from the said viewpoint.

The methacrylic polymer (b) may further contain a structural unit derived from another monomer copolymerizable with methacrylic acid ester. For the example of another monomer which can be copolymerized, Acrylic acid ester, such as methyl acrylate, ethyl acrylate, and n-butyl acrylate; (meth)acrylic monomers (ring-containing (meth)acrylic monomers) having an alicyclic ring, a heterocyclic ring or an aromatic ring such as benzyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and phenoxyethyl (meth)acrylate are included.

It is preferable that it is 50 mass % or less with respect to all the structural units which comprise a methacrylic polymer (b), and, as for content of the structural unit derived from the monomer which can be copolymerized, it is more preferable that it is 30 mass % or less.

In this embodiment, when the base film is not stretched, the rubber particles may have a shape close to a spherical shape. That is, the aspect ratio of the rubber particles when observing the cross section or surface of the base film may be about 1 to 2.

It is preferable that the range of the average particle diameter of a rubber particle is 100-400 nm. When the average particle diameter of the rubber particles is 100 nm or more, it is easy to impart sufficient toughness and stress relaxation properties to the base film, and when it is 400 nm or less, the transparency of the base film is less likely to be impaired. The average particle diameter of the rubber particles is more preferably in the range of 150 to 300 nm from the same viewpoint.

The average particle diameter of a rubber particle is computable with the following method.

The average particle diameter of rubber particles can be measured as an average value of equivalent circle diameters of 100 particles obtained by SEM imaging or TEM imaging of the surface or slice of the base film. The equivalent circle diameter can be obtained by converting the projected area of the particle obtained by imaging into the diameter of a circle having the same area. At this time, rubber particles observed by SEM observation and/or TEM observation at a magnification of 5000 are used for calculation of the average particle diameter.

The content of the rubber particles is not particularly limited, but is preferably in the range of 40 to 85% by mass, and more preferably in the range of 45 to 75% by mass with respect to the base film.

<Cycloolefin resin>

It is preferable that the cycloolefin resin used for the base film is a polymer of a cycloolefin monomer or a copolymer of a cycloolefin monomer and a copolymerizable monomer other than that.

The cycloolefin monomer is preferably a cycloolefin monomer having a norbornene skeleton, and more preferably a cycloolefin monomer having a structure represented by the following general formula (A-1) or (A-2).

[Formula 1]

In the general formula (A-1), R ¹ to R ⁴ each independently represent a hydrogen atom, a hydrocarbon group of 1 to 30 carbon atoms, or a polar group. p represents an integer of 0 to 2; However, it is assumed that all of R ¹ to R ⁴ do not simultaneously represent a hydrogen atom, R ¹ and R ² do not simultaneously represent a hydrogen atom, and R ³ and R ⁴ do not simultaneously represent a hydrogen atom.

The hydrocarbon group having 1 to 30 carbon atoms represented by R ¹ to R ⁴ in the general formula (A-1) is, for example, preferably a hydrocarbon group having 1 to 10 carbon atoms, and 1 to 5 carbon atoms. It is more preferable that it is a hydrocarbon group of The hydrocarbon group of 1 to 30 carbon atoms may further have a linking group containing, for example, a halogen atom, an oxygen atom, a nitrogen atom, a sulfur atom, or a silicon atom. Examples of such a linking group include divalent polar groups such as a carbonyl group, an imino group, an ether bond, a silyl ether bond, and a thioether bond. Examples of the hydrocarbon group having 1 to 30 carbon atoms include a methyl group, an ethyl group, a propyl group and a butyl group.

Examples of the polar group represented by R ¹ to R ⁴ in the general formula (A-1) include a carboxy group, a hydroxy group, an alkoxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group and a cyano group. Especially, a carboxy group, a hydroxy group, an alkoxycarbonyl group, and an aryloxycarbonyl group are preferable, and an alkoxycarbonyl group and an aryloxycarbonyl group are preferable from the viewpoint of ensuring the solubility at the time of solution film formation.

It is preferable that p in General formula (A-1) is 1 or 2 from a viewpoint of improving the heat resistance of an optical film. It is because when p is 1 or 2, the polymer obtained becomes bulky and the glass transition temperature tends to improve. In addition, there is also an advantage that it becomes slightly responsive to humidity and it becomes easy to control the curl balance as a laminate.

[Formula 2]

In the general formula (A-2), R ⁵ represents a hydrogen atom, a hydrocarbon group of 1 to 5 carbon atoms, or an alkylsilyl group having an alkyl group of 1 to 5 carbon atoms. R ⁶ represents a carboxy group, a hydroxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, a cyano group, or a halogen atom (fluorine atom, chlorine atom, bromine atom or iodine atom). p represents an integer of 0 to 2;

R ⁵ in the general formula (A-2) preferably represents a hydrocarbon group of 1 to 5 carbon atoms, and more preferably represents a hydrocarbon group of 1 to 3 carbon atoms.

R ⁶ in the general formula (A-2) preferably represents a carboxy group, a hydroxy group, an alkoxycarbonyl group, and an aryloxycarbonyl group, and from the viewpoint of ensuring solubility during solution film formation, an alkoxycarbonyl group and an aryloxycarbonyl group more preferable

It is preferable that p in General formula (A-2) represents 1 or 2 from a viewpoint of improving the heat resistance of an optical film. It is because when p represents 1 or 2, the polymer obtained becomes bulky and the glass transition temperature tends to improve.

A cycloolefin monomer having a structure represented by general formula (A-2) is preferable from the viewpoint of improving solubility in organic solvents. In general, since crystallinity of an organic compound is reduced by breaking symmetry, solubility in organic solvents is improved. Since R ⁵ and R ⁶ in the general formula (A-2) are substituted only with the ring-constituting carbon atoms on one side with respect to the axis of symmetry of the molecule, the symmetry of the molecule is low, that is, represented by the general formula (A-2) Since the cycloolefin monomer having a structure has high solubility, it is suitable when manufacturing an optical film by a solution casting method.

The content ratio of the cycloolefin monomer having a structure represented by the general formula (A-2) in the polymer of the cycloolefin monomer is, for example, 70 mol% with respect to the total of all cycloolefin monomers constituting the cycloolefin resin. or more, preferably 80 mol% or more, more preferably 100 mol%. When the cycloolefin monomer having a structure represented by the general formula (A-2) is included at least a certain level, the orientation of the resin increases, so that the phase difference (retardation) value tends to increase.

Hereinafter, specific examples of the cycloolefin monomer having a structure represented by general formula (A-1) are shown in exemplified compounds 1 to 14, and specific examples of cycloolefin monomer having a structure represented by general formula (A-2) are exemplified compounds It shows to 15-34.

[Formula 3]

Examples of the copolymerizable monomer copolymerizable with the cycloolefin monomer include a copolymerizable monomer capable of ring-opening copolymerization with the cycloolefin monomer and a copolymerizable monomer capable of addition copolymerization with the cycloolefin monomer.

Examples of the copolymerizable monomer capable of ring-opening copolymerization include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene and dicyclopentadiene.

Examples of the copolymerizable monomer capable of addition copolymerization include unsaturated double bond-containing compounds, vinyl-based cyclic hydrocarbon monomers, and (meth)acrylates. Examples of the unsaturated double bond-containing compound include olefin compounds having 2 to 12 (preferably 2 to 8) carbon atoms, and examples thereof include ethylene, propylene, and butene. Examples of the vinyl-based cyclic hydrocarbon monomer include vinylcyclopentene-based monomers such as 4-vinylcyclopentene and 2-methyl-4-isopropenylcyclopentene. Examples of (meth)acrylates include alkyl (meth)acrylates having 1 to 20 carbon atoms, such as methyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate. do.

The content ratio of the cycloolefin monomer in the copolymer of the cycloolefin monomer and the copolymerizable monomer is, for example, 20 to 80 mol%, preferably 30 to 70 mol%, based on the total of all monomers constituting the copolymer. can be done within the range of

As described above, the cycloolefin-based resin is obtained by polymerizing or copolymerizing a cycloolefin monomer having a norbornene skeleton, preferably a cycloolefin monomer having a structure represented by general formula (A-1) or (A-2). It is a polymer obtained, and the following are contained in the example.

1) Ring-opening polymers of cycloolefin monomers

2) A ring-opening copolymer of a cycloolefin monomer and a copolymerizable monomer capable of ring-opening copolymerization therewith

3) Hydrogenated product of the ring-opening (co)polymer of 1) or 2) above

4) A (co)polymer obtained by cyclization of the ring-opening (co)polymer of 1) or 2) by Friedel Crafts reaction and then hydrogenation

5) Saturated copolymers of cycloolefin monomers and compounds containing unsaturated double bonds

6) Addition copolymers of cycloolefin monomers with vinyl-based cyclic hydrocarbon monomers and hydrogenated products thereof

7) Alternating copolymer of cycloolefin monomer and (meth)acrylate

All of the above 1) to 7) polymers can be obtained by a known method, for example, a method described in Japanese Unexamined Patent Publication No. 2008-107534 or Japanese Unexamined Patent Publication No. 2005-227606. For example, as the catalyst and solvent used for the ring-opening copolymerization in the above 2), those described in Paragraphs 0019 to 0024 of Unexamined-Japanese-Patent No. 2008-107534 can be used, for example. The catalyst used for the hydrogenation of said 3) and 6) can use the thing of Paragraph 0025 of Unexamined-Japanese-Patent No. 2008-107534 - 0028, for example. As the acidic compound used in the Friedel Crafts reaction of the above 4), for example, those described in paragraph 0029 of JP-A-2008-107534 can be used. As the catalyst used for the addition polymerization of the above 5) to 7), for example, those described in Paragraphs 0058 to 0063 of Unexamined-Japanese-Patent No. 2005-227606 can be used. The alternating copolymerization reaction of said 7) can be performed by the method described in Paragraphs 0071 and 0072 of Unexamined-Japanese-Patent No. 2005-227606, for example.

Especially, the polymer of said 1)-3) and 5) is preferable, and the polymer of said 3) and 5) is more preferable. That is, the cycloolefin-based resin has a structural unit represented by the following general formula (B-1) and a general formula (B -2) preferably contains at least one of the structural units represented by the general formula (B-2), or only the structural unit represented by the general formula (B-1) is represented by the general formula (B-1) It is more preferable to include both of the structural units represented by 2). The structural unit represented by the general formula (B-1) is a structural unit derived from the cycloolefin monomer represented by the general formula (A-1) described above, and the structural unit represented by the general formula (B-2) is represented by the general formula described above. It is a structural unit derived from the cycloolefin monomer represented by (A-2).

[Formula 4]

In general formula (B-1), X represents -CH=CH- or -CH ₂ CH ₂ -. R ¹ to R ⁴ and p have the same meaning as R ¹ to R ⁴ and p in general formula (A-1), respectively.

[Formula 5]

In general formula (B-2), X represents -CH=CH- or -CH ₂ CH ₂ -. R ⁵ to R ⁶ and p have the same meaning as R ⁵ to R ⁶ and p in the general formula (A-2), respectively.

A commercial item may be sufficient as the cycloolefin resin used for this invention. Examples of commercially available cycloolefin resins include Arton G (eg, G7810, etc.), Arton F, Arton R (eg, R4500, R4900, and R5000), and Arton, manufactured by JSR Co., Ltd. RX (eg RX4500, etc.) is included.

The intrinsic viscosity [η]inh of the cycloolefin resin is preferably in the range of 0.2 to 5 cm 3 /g, more preferably in the range of 0.3 to 3 cm 3 /g, and 0.4 to 1.5, measured at 30 ° C. It is more preferably in the range of cm 3 /g.

The number average molecular weight (Mn) of the cycloolefin resin is preferably in the range of 8000 to 100000, more preferably in the range of 10000 to 80000, still more preferably in the range of 12000 to 50000. The weight average molecular weight (Mw) of the cycloolefin resin is preferably in the range of 20000 to 300000, more preferably in the range of 30000 to 250000, still more preferably in the range of 40000 to 200000. The number average molecular weight and weight average molecular weight of cycloolefin resin can be measured in terms of polystyrene by the above-mentioned gel permeation chromatography (GPC).

When the intrinsic viscosity [η]inh, number average molecular weight, and weight average molecular weight are within the above ranges, the heat resistance, water resistance, chemical resistance, mechanical properties, and moldability of the cycloolefin resin as a base film become good.

The glass transition temperature (Tg) of the cycloolefin resin is usually 110 ° C. or higher, preferably in the range of 110 to 350 ° C., more preferably in the range of 120 to 250 ° C., and in the range of 120 to 220 ° C. it is more preferable When the Tg is 110°C or higher, deformation under high-temperature conditions is easily suppressed. On the other hand, when the Tg is 350°C or less, the molding process becomes easy, and the deterioration of the resin due to heat during the molding process is also easily suppressed.

It is preferable that it is 70 mass % or more with respect to a base film, and, as for content of cycloolefin type resin, it is more preferable that it is 80 mass % or more.

<fine particles>

When the base film according to the present invention uses a cycloolefin-based resin, it is also preferable to contain fine particles.

Examples of the fine particles used in the present invention include inorganic compounds such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, and aluminum silicate. , magnesium silicate and calcium phosphate. Moreover, microparticles|fine-particles of an organic compound can also be used suitably. Examples of organic compounds include polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropyl methacrylate, polymethyl acrylate, polyethylene carbonate, acrylic styrene-based resin, silicone-based resin, polycarbonate resin, and benzogua. It is synthesized by pulverization and suspension polymerization of organic polymer compounds such as namine-based resins, melamine-based resins, polyolefin-based powders, polyester-based resins, polyamide-based resins, polyimide-based resins, polyfluoroethylene-based resins, and starch. A single polymer compound may be used.

The microparticles preferably contain silicon from the viewpoint of lowering turbidity, and silicon dioxide is particularly preferred, for example, Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above manufactured by Nippon Aerosil Co., Ltd.) is commercially available and can be used.

<Polyimide-based resin>

The polyimide-based resin may be a polymerization product of tetracarboxylic dianhydride and diamine.

Any of aromatic tetracarboxylic dianhydride, aliphatic tetracarboxylic dianhydride, and alicyclic tetracarboxylic dianhydride may be sufficient as tetracarboxylic dianhydride, Preferably it is aromatic tetracarboxylic dianhydride. Diamine may be any of aromatic diamine, aliphatic diamine, and alicyclic diamine, but is preferably aromatic diamine.

The weight average molecular weight Mw of the polyimide resin is not particularly limited, but is preferably 100,000 to 300,000, and is in the range of 130,000 to 250,000 from the viewpoint of increasing the toughness of the base film and making it difficult to break due to conveying tension. more preferable The measuring method of the weight average molecular weight Mw of polyimide-type resin is the same as the above.

It is preferable that it is 60 mass % or more with respect to the base film, and, as for content of polyimide-type resin, it is more preferable that it is 70 mass % or more.

[1.3] Physical properties

<Phase difference Ro and Rt>

The base film according to the present invention can be laminated on the surface of a polarizer and function as an optical film such as a retardation film.

From the viewpoint of using the base film as, for example, a retardation film for IPS mode, the retardation Ro in the in-plane direction measured at a measurement wavelength of 590 nm and in an environment of 23 ° C. 55% RH is in the range of 0 to 10 nm It is preferable, and it is more preferable that it is the range of 0-5 nm. The retardation Rt in the thickness direction of the base film is preferably in the range of -40 to 40 nm, and more preferably in the range of -25 to 25 nm.

Ro and Rt are each defined by the following formula.

(In the expression,

_nx represents the refractive index in the in-plane slow axis direction (the direction in which the refractive index becomes the maximum) of the base film,

n _y represents the refractive index in the direction orthogonal to the in-plane slow axis of the base film,

n _z represents the refractive index in the thickness direction of the base film,

d represents the film thickness (nm) of the base film.)

The in-plane slow axis of the base film can be confirmed by an automatic birefringence meter axo scan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axo Matrix Co., Ltd.).

Ro and Rt can be measured by the following method.

1) Humidity is controlled for 24 hours for a base film in the environment of 23 degreeC and 55 %RH. The average refractive index of this film is measured with an Abbe refractometer, and the film thickness d is measured using a commercially available micrometer.

2) The retardation Ro and Rt of the film after humidity control at a measurement wavelength of 590 nm were measured using an automatic birefringence meter Axo Scan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axo Matrix Co., Ltd.) at 23 ° C. 55% RH. measured under the environment.

The phase difference Ro and Rt of the base film can be adjusted by, for example, the type of resin, stretching conditions, and drying conditions. For example, Rt can be made low by making drying temperature high.

[1.4] Manufacturing method of base film

The shape of the base film according to the present invention is not particularly limited, but may be, for example, a strip shape. That is, it is preferable that the base film concerning this invention is wound up in roll shape in the direction orthogonal to the width direction, and it is set as a roll body.

[Manufacturing method]

The manufacturing method of the base film which concerns on this invention includes 1) the process of obtaining the base film solution, 2) the process of applying the obtained base film solution to the surface of a support body, and 3) removing a solvent from the provided base film solution. It has a process of removing and forming a base film.

1) Process of obtaining solution for base film

A solution (also referred to as "dope") for a base film containing the above resin and a solvent is prepared.

The solvent used for the solution for the base film may be one capable of favorably dispersing or dissolving the resin, and is not particularly limited. For example, as the organic solvent used in the present invention, alcohols (methanol, ethanol, diol, triol, tetrafluoropropanol, etc.), glycols, cellosolves, ketones (acetone, methyl ethyl ketone, etc.), Carboxylic acids (formic acid, acetic acid, etc.), carbonates (ethylene carbonate, propylene carbonate, etc.), esters (ethyl acetate, propyl acetate, etc.), ethers (isopropyl ether, THF, etc.), amides (dimethyl sulfoxide, etc.) ), hydrocarbons (heptane, etc.), nitriles (acetonitrile, etc.), aromatics (cyclohexylbenzene, toluene, xylene, chlorobenzene, etc.), halogenated alkyls (dichloromethane (also referred to as "methylene chloride"), etc. ), amines (1,4-diazabicyclo[2.2.2]octane, diazabicycloundecene, etc.), lactones, and the like.

Among them, as the solvent for the base film, the boiling point is 100° C. or less under atmospheric pressure, the kind is a chlorine-based solvent, and more specifically, dichloromethane (also referred to as “methylene chloride”) is the dope for the base film. When preparing and forming into a film, it is preferable from the viewpoint of ease of handling. This is preferable from the viewpoint of high solubility and high drying rate, and thus the film quality of the coating film can be adjusted when forming a film by preparing dope for a base film. A hydrophilic solvent may also be added. Although ketones and alcohols are mentioned as a hydrophilic solvent, Alcohols are preferable. More preferred are isopropanol, ethanol, methanol and the like, and most preferred is methanol. As an addition amount, the range of 1-20 mass % is preferable, and it is the range of 3-10 mass % more preferably.

It is preferable that it is the range of 1.0-20 mass %, for example from a viewpoint which makes it easy to adjust the viscosity to the range mentioned later as for the resin density|concentration of the solution for base films. From the viewpoint of reducing the amount of shrinkage during drying of the coating film, the resin concentration of the base film solution is preferably moderately high, more preferably greater than 5% by mass and less than or equal to 20% by mass, and still more preferably greater than 5% by mass and less than or equal to 15% by mass. desirable. In addition, by adjusting the concentration of the solution, the time until the film is formed is shortened, and their drying time can also be used as a means to control the surface state of the base film. For high concentration, you may use a mixed solvent suitably.

The viscosity of the base film solution may be to a level capable of forming a base film having a desired film thickness, and is not particularly limited. For example, it is preferably in the range of 5 to 5000 mPa·s. When the viscosity of the solution for base film is 5 mPa·s or more, it is easy to form a base film having an appropriate film thickness, and when it is 5000 mPa·s or less, the occurrence of film thickness nonuniformity can be suppressed due to an increase in the viscosity of the solution. . As for the viscosity of the solution for base films, it is more preferable that it is the range of 100-1000 mPa*s from the same viewpoint. The viscosity of the solution for base films can be measured at 25°C with an E-type viscometer.

2) Process of applying solution for base film

Next, the obtained solution for base films is applied to the surface of the support. Specifically, the obtained solution for base films is applied to the surface of a support. A laminated body of a support body and a base film is also referred to as "laminated film".

<support>

A support body supports at the time of formation of a base film, and usually contains a resin film. It is preferable that the film thickness of a support body is 50 micrometers or less. The film thickness of the support is preferably in the range of 15 to 45 μm, more preferably in the range of 20 to 40 μm, since a certain level of strength (elasticity and rigidity) is required as the support even though it is a thin film.

Examples of the resin used include cellulose ester-based resins, cycloolefin-based resins, polypropylene-based resins, acrylic resins, polyester-based resins, polyarylate-based resins, and styrene-based resins or composite resins thereof, among which high humidity It is preferable to use a polyester-based resin as a resin excellent in storageability in the environment.

Examples of the resin film include polyester-based resins (eg, polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene, etc.) phthalates (PBN), etc.) and the like. Among them, a polyester-based resin film containing polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) is preferable from the viewpoint of ease of handling.

The resin film may be heat treated (heat relaxed) or stretched.

The heat treatment is for reducing the residual stress of the resin film (for example, residual stress accompanying stretching) and is not particularly limited, but when the glass transition temperature of the resin constituting the resin film is Tg, (Tg + 60) to (Tg + 180) °C.

The stretching treatment is for increasing the residual stress of the resin film, and it is preferable to perform the stretching treatment in the biaxial direction of the resin film, for example. The stretching treatment can be performed under arbitrary conditions, and can be performed at, for example, a stretching ratio of about 120 to 900%. Whether or not the resin film is stretched can be confirmed, for example, by whether or not there is an in-plane stratum axis (an axis extending in a direction in which the refractive index is maximized). The stretching treatment may be performed before or after lamination of the base film, but it is preferable that the stretching is performed before lamination.

A commercially available product can be used for the polyester resin film (simply referred to as a polyester film). For example, polyethylene terephthalate film TN100 (manufactured by Toyobo Co., Ltd.), MELINEX ST504 (manufactured by Teijin Dupont Film Co.), etc. are preferable. can be used

The support body may further have a mold release layer formed on the surface of the resin film. A release layer can make it easy to peel a support body from a base film when manufacturing a cover member.

The release layer may contain a known release agent and is not particularly limited. Examples of release agents included in the release layer include silicone release agents and non-silicone release agents.

Examples of the silicone-based release agent include known silicone-based resins. Examples of non-silicone-based release agents include long-chain alkyl pendant-type polymers obtained by reacting long-chain alkyl isocyanates with polyvinyl alcohol or ethylene-vinyl alcohol copolymers, and olefin-based resins (eg copolymerized polyethylene, cyclic polyolefin, polymethylpentene). , polyarylate resins (for example, polycondensates of aromatic dicarboxylic acid components and dihydric phenol components), fluororesins (for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), poly Vinyl Fluoride (PVF), PFA (copolymer of tetrafluoroethylene and perfluoroalkoxyethylene), FEP (tetrafluoroethylene and hexafluoropropylene copolymer), ETFE (tetrafluoroethylene and ethylene copolymer) ), etc. are included.

The thickness of the release layer is not particularly limited as long as it can express the desired peelability, but is preferably in the range of, for example, 0.1 to 1.0 μm.

The support may contain a plasticizer as an additive. The plasticizer is not particularly limited, but is preferably a polyhydric alcohol ester plasticizer, a phthalate ester plasticizer, a citric acid plasticizer, a fatty acid ester plasticizer, a phosphate ester plasticizer, a polyhydric carboxylic acid ester plasticizer, and a polyester plasticizer. It is preferable to select from etc.

Further, the support may contain a UV absorber. Examples of the ultraviolet absorber used include those of the benzotriazole type, 2-hydroxybenzophenone type, or salicylic acid phenyl ester type. For example, 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole , triazoles such as 2-(3,5-di-t-butyl-2-hydroxyphenyl)benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzo Benzophenones, such as phenone and 2,2'- dihydroxy- 4-methoxy benzophenone, can be illustrated.

Further, the support used in the present invention preferably contains fine particles in order to improve transportability.

Examples of the fine particles include inorganic compounds such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and phosphoric acid. Calcium may be included. Moreover, microparticles|fine-particles of an organic compound can also be used suitably. Examples of organic compounds include polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropyl methacrylate, polymethyl acrylate, polyethylene carbonate, acrylic styrene-based resin, silicone-based resin, polycarbonate resin, and benzogua. It is synthesized by pulverization and suspension polymerization of organic polymer compounds such as namine-based resins, melamine-based resins, polyolefin-based powders, polyester-based resins, polyamide-based resins, polyimide-based resins, polyfluoroethylene-based resins, and starch. A single polymer compound may be used.

The microparticles preferably contain silicon from the viewpoint of lowering turbidity, and silicon dioxide is particularly preferred, for example, Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above manufactured by Nippon Aerosil Co., Ltd.) is commercially available and can be used.

As the method for producing the support used in the present invention, a conventional inflation method, T-die method, calender method, cutting method, casting method, emulsion method, hot press method, etc. can be used. From the viewpoints of suppression of optical defects such as die lines, etc., the film forming method is preferably a solution casting method or a melt casting method. In addition, in the case of the solution casting method, the temperature in the processing step is low, and for this reason, high functionality can be provided by using various additives.

In the case of forming a film by a solution casting method, the method for producing a support body includes a step of dissolving and dispersing a thermoplastic resin and additives such as the above-mentioned fine particles in a solvent to prepare a dope (dissolution step; dope preparation step), and infinite dope A process of casting on an endless metal support to be transferred (casting process), a process of drying flexible dope as a web (solvent evaporation process), a process of peeling from a metal support (peeling process), a process of drying, stretching, and maintaining width ( It is preferable to include the process of extending|stretching, width holding|maintenance, drying process), and winding up the finished film in roll shape (winding-up process).

It is preferable to form the base film concerning this invention by the following method using the support body manufactured as mentioned above.

The coating method of the base film solution is not particularly limited, and may be a known method such as a back roll coating method, a gravure coating method, a spin coating method, a wire bar coating method, a roll coating method, or the like. Among them, the back coating method is preferable from the viewpoint of being able to form a thin and uniform coating film.

3) Process of forming a base film

Then, the solvent is removed from the base film solution applied to the support to form a base film.

Specifically, the solution for base films applied to the support is dried. Drying can be performed, for example, by blowing or heating. Among them, from the viewpoint of making it easy to suppress the curl of the base film, etc., it is preferable to dry by blowing, and furthermore, providing a difference in wind speed between the initial drying stage and the latter stage of drying controls the following film thickness variation. It is desirable to have Specifically, the film thickness variation tends to increase when the initial wind speed is high, and decrease when the initial wind speed is low.

Therefore, by adjusting the drying conditions (for example, drying temperature, drying air volume, drying time, etc.), the coarseness of the base film can be controlled, and the film thickness of the base film can be adjusted so as to satisfy the following formula 1. .

Equation 1: 5 < |Average value of film thicknesses of three randomly selected points in the width direction (B) - Average film thickness value (A)|/Average film thickness value (A) × 100 < 20 (%)

Here, the average film thickness value (A) is the average value of the film thickness values of 10 points randomly extracted from the film.

When the value represented by Formula 1 exceeds 5%, the effect of improving adhesion with the upper layer can be obtained by having the surface moderately uneven, and when the value is less than 20%, the unevenness of the surface is not too large, and the upper layer It does not affect applicability or smoothness.

For the measurement of the film thickness, a commercially available film thickness step measuring device can be used. For example, as a film thickness measuring system, F20-UV (manufactured by Filmetrix Co., Ltd.) can be used.

Moreover, it is preferable to adjust the variation of the film thickness of the said base film within the range of 0.5 +/- 0.2 micrometer. It is preferable to adjust the film quality in the direction of becoming coarse from the viewpoint of improving adhesion with the upper layer, specifically, it is preferable to increase the drying rate, preferably 0.0015 to 0.05 kg / hr m 2, and 0.002 to 0.05 kg It is more preferable that it is the range of /hr*m<2>.

The drying rate is expressed as the mass of the solvent evaporated per unit time per unit area. A drying rate can normally be adjusted according to drying temperature. The drying temperature may be, for example, in the range of 50 to 200°C ((Tb - 50) to (Tb + 50)°C with respect to the boiling point Tb of the solvent to be used, although it also varies depending on the type of solvent used. Temperature control may be performed in multiple steps. After drying has progressed to some extent, drying speed and film quality can be controlled by drying at a higher temperature.

As described above, the base film related to this embodiment may be strip-shaped. Therefore, it is preferable that the manufacturing method of the laminated|multilayer film which concerns on this embodiment further includes the process of winding up 4) strip-like laminated|multilayer film in roll shape, and using it as a roll body.

4) Process of winding up a base film to obtain a roll body

The obtained strip-shaped base film is wound up in a roll shape in a direction orthogonal to the width direction to obtain a roll body.

The length of the strip-shaped base film is not particularly limited, but may be, for example, about 100 to 10000 m. Moreover, it is preferable that it is 1 m or more, and, as for the width|variety of a strip-shaped laminated|multilayer film, it is more preferable that it is the range of 1.1-4 m. From the viewpoint of enhancing the uniformity of the film, it is more preferably in the range of 1.3 to 2.5 m.

[Manufacturing device]

The manufacturing method of the base film used for this invention can be implemented with the manufacturing apparatus shown in FIG. 3, for example.

3 is a schematic diagram of a manufacturing apparatus B200 for implementing the manufacturing method of the base film according to the present embodiment. Manufacturing apparatus B200 includes a supply unit B210, an application unit B220, a drying unit B230, a cooling unit B240, and a take-up unit B250. Ba to Bd represent conveying rolls that convey the support (B110).

Supply unit B210 has a feeding device (not shown) that feeds roll B201 of strip-shaped support B110 wound around a core.

The applicator (B220) is an applicator, comprising: a backup roll (B221) holding the support (B110); and an application head (B222) that applies the base film solution to the support (B110) held by the backup roll (B221). ) and a decompression chamber (B223) formed upstream of the application head (B222).

The flow rate of the solution for base films discharged from the application head B222 can be adjusted by a pump not shown. The flow rate of the base film solution discharged from the coating head B222 is set to an amount that can stably form a coating layer having a predetermined film thickness when continuously applied under the previously adjusted conditions of the coating head B222. there is.

The decompression chamber (B223) is a mechanism for stabilizing the bead (puddle of the coating liquid) formed between the base film solution from the application head (B222) and the support (B110) at the time of application, so that the degree of decompression can be adjusted. has been The decompression chamber B223 is connected to a decompression blower (not shown), and the inside is depressurized. The decompression chamber (B223) is in a state where there is no air leakage, and the gap with the backup roll is also adjusted to be narrow, so that a bead of a stable coating liquid can be formed.

The drying unit B230 is a drying device for drying the coating film applied to the surface of the support body B110, and has a drying chamber B231, a drying gas inlet B232, and an outlet B233. The temperature and air volume of the drying air are appropriately determined depending on the type of coating film and the type of support (B110). The amount of residual solvent in the dried coating film can be adjusted by setting conditions such as the temperature and air volume of the drying air and the drying time in the drying unit B230. The residual solvent amount of the coating film after drying can be measured by comparing the unit mass of the coating film after drying with the mass after sufficiently drying the coating film.

(residual solvent amount)

Since a base film is obtained by apply|coating the solution for base films, the solvent derived from the said solution may remain. The amount of residual solvent can be controlled by the concentration of the solvent/coating solution used, the wind speed used to dry the base film, the drying temperature/time, the conditions of the drying room (whether outside air or indoor circulation), and the heating temperature of the back roll at the time of application. .

As described above, high-speed drying makes the film coarse and can control the surface condition.

The amount of residual solvent in the base film preferably satisfies the following formula 2 when the amount of residual solvent in the base film is set as S ₁ , from the viewpoint of the curl balance of the base film.

Formula 2: 10 < S ₁ < 1000 (ppm)

Specifically, the residual solvent amount of the base film is more preferably less than 800 ppm, and more preferably from 500 to less than 700 ppm, considering the curl balance of the base film. Moreover, the adhesiveness of a support body and a base film improves by selecting the solvent and application|coating process which a solvent remains also in a support body. The amount of residual solvent in the support is preferably in the range of 10 to 100 ppm.

The amount of residual solvent in the support and base film can be measured by head space gas chromatography. In the head space gas chromatography method, a sample is sealed in a container, heated, and the gas in the container is rapidly injected into a gas chromatograph while the container is filled with volatile components, mass spectrometry is performed, and the It is to quantify volatile components while performing identification. In the head space method, while making it possible to observe all peaks of volatile components with a gas chromatograph, by using an analysis method using electromagnetic interaction, volatile substances and monomers can also be quantified with high accuracy. can

The cooling part (B240) cools the temperature of the support (B110) having the coating film (base film) obtained by drying in the drying part (B230) and adjusts it to an appropriate temperature. The cooling section B240 has a cooling chamber B241, a cooling air inlet B242, and a cooling air outlet B243. The temperature and air volume of the cooling air can be appropriately determined depending on the type of coating film and the type of support (B110). In addition, even if the cooling unit B240 is not provided, the cooling unit B240 may not be provided in the case where the cooling temperature is appropriate.

The winding unit B250 is a winding device (not shown) for winding the support body B110 on which the base film is formed to obtain the roll body B251.

[2] Transparent substrate

Here, "transparent" refers to a total light transmittance of 80% or more, preferably 85% or more, more preferably 90% or more, particularly preferably 95% or more, as measured after humidity control in an environment of 23°C/55%RH. . The total light transmittance can be measured in accordance with JIS 7573 (Plastic - method for determining total light transmittance and total light reflectance).

The transparent substrate according to the present invention is a flexible transparent substrate having a thickness of 5 μm or more and less than 50 μm. If the thickness is less than 5 μm, since the strength cannot be maintained, the rate of breakage during processing is high, the yield rapidly deteriorates, and durability is deteriorated, such as breakage accompanying repeated opening and closing of the display. In addition, if the thickness is 50 μm or more, the overall thickness of the cover member becomes too thick, resulting in poor flexibility (occurrence of cracks, etc.), weight, and the like, so it is necessary to fall within the above range. As a more preferable thickness, they are 10 micrometers or more and less than 30 micrometers.

Further, the elastic modulus of the transparent substrate according to the present invention is within the range of 55 to 80 GPa, and the value of the ratio of the elastic modulus of the transparent substrate to the elastic modulus of the substrate film (elastic modulus of the transparent substrate/elastic modulus of the substrate film) is 30 or more. it is desirable This is to use a base film having a lower elastic modulus, that is, to use a base film having a lower elastic modulus, that is, to provide a cover member that does not cause improvement in press-fit strength or crease by using a transparent base material having a low elastic modulus due to thinning. By setting the value of (elastic modulus of the transparent substrate/elastic modulus of the base film) to 30 or more, the protective function of the transparent substrate can be further improved.

<Measurement of modulus of elasticity>

The measurement conditions for the elastic modulus (also referred to as tensile elastic modulus) of the base film and the transparent substrate are set as follows, and the elastic modulus is determined by linear regression between strains of 0.05 to 0.25%.

About MD direction, based on JISK7127 (1999), tensile elasticity modulus is measured by the following method.

1) A substrate film or a transparent substrate is cut out to a size of 100 mm (MD direction) x 10 mm (TD direction) to obtain a test piece.

2) This test piece was stretched at a tensile rate of 50 mm/min in the longitudinal direction (MD direction) of the test piece at a distance between chucks of 50 mm using Tensilon RTC-1225A manufactured by Orientec, and the tensile elastic modulus in the MD direction to measure The measurement is performed at 23°C and 55% RH.

[2.1] glass substrate

From the standpoint of excellent durability, flatness, etc., the transparent base material according to the present invention is preferably a thin glass base material, examples of which include soda lime glass and silicate glass, preferably silicate glass. As, it is more preferable that they are silica glass or borosilicate glass.

It is preferable that the glass which comprises a glass substrate is an alkali-free glass which does not substantially contain an alkali component, and specifically, it is glass whose content of an alkali component is 1000 ppm or less. It is preferable that it is 500 ppm or less, and, as for content of the alkali component in a glass substrate, it is more preferable that it is 300 ppm or less. In the glass base material containing an alkali component, substitution of cations occurs on the surface of the film, and the phenomenon of soda blow is likely to occur. This is because the density of the surface layer of the film tends to decrease and the glass substrate is easily damaged.

The glass substrate can be formed by a generally known method, for example, a float method, a down draw method, an overflow down draw method, or the like. Especially, the overflow down-draw method is preferable from the viewpoint that the surface of the glass substrate does not come into contact with the molding member during molding and the surface of the resulting glass substrate is less likely to be damaged.

The glass base material used in the present invention can be obtained by grinding thick glass such as borosilicate glass to a desired thickness, but it is difficult to obtain a glass base material of less than 200 μm by grinding and polishing a thick glass sheet. .

Therefore, in order to obtain a glass substrate having a thickness of 5 μm or more and less than 50 μm according to the present invention, it is preferable to employ a special float method.

The thinner the thickness, the more difficult the handling and processing of the ultra-thin glass plate, the lower the strength of the glass, and the higher the probability of breakage. In order to facilitate handling and processing of the thin glass substrate, the thin glass substrate is processed while temporarily adhering to a thicker support substrate (hereinafter also referred to as a “carrier substrate”), and the support substrate is processed as a post-process. A method of obtaining a thin glass substrate by peeling has been proposed.

For example, according to International Publication No. 2017/066924 described above, soda lime glass having a thickness of less than 100 µm can be manufactured by the following process.

(Step 1) A contact film (“contact film”) formed on a glass carrier substrate having a bonding surface so that the first surface of the surface of the glass substrate 22 is in contact with the second surface on the opposite side to the first surface. It is also called.) process of attaching.

That is, as shown in FIG. 4 (Step 1), in the manufacturing method of the glass substrate, a material for forming a glass substrate is poured into a carrier substrate 21 having sufficient strength and a thickness that is easy to process to a desired thickness, and glass After forming the first surface of the substrate 22 so as to be in contact with the carrier substrate 21, a step of attaching the contact film 23 to the second surface on the opposite side of the glass substrate 22 is provided.

(Process 2) Then, the process of peeling the glass base material 22 from the carrier substrate 21 with the contact film 23 with high adhesive force (FIG. 4 (process 2)).

(Step 3) A step of removing the contact film 23 from the second surface of the glass substrate 22 separated from the carrier substrate by a weakening treatment (electron irradiation 24) that weakens the adhesive strength of the contact film (Fig. 4 (step 3)).

That is, by using the contact film 23 for safely holding the glass substrate, it is possible to have a protective function of the glass substrate 22, and thus, for example, the exposed surface of the glass substrate 22, For example, it can be protected from possible mechanical damage, and can be handled safely and conveniently.

The contact film may include a hard or soft material, depending on specific requirements, and polyethylene terephthalate (PET), polyethylene (PE) or polyolefin (PO) may be used as a preferred material.

The contact film is usually adhered to the glass substrate by an adhesive layer composed of an adhesive formed on one surface of the substrate. However, it is not excluded that the base material of the contact film itself has adhesiveness.

The adhesive strength between the contact film and the second surface of the glass substrate is selected such that sufficient force can be transmitted to the glass substrate during peeling by the peeling device in order to dissolve the bonding force between the carrier substrate and the glass substrate during compression.

The contact film can be provided as a foil or tape, which can be wound from a roll, for example, or can be provided as a sheet. Preferably, the thickness of the contact film is 50 μm or more, more preferably 80 μm or more, still more preferably 125 μm or more, and particularly preferably 150 μm or more.

As described above, the glass substrate is preferably made of an alkali-containing glass composition. Preferred glass materials are, for example, lithium aluminosilicate glass, soda lime glass, borosilicate glass, alkali metal aluminosilicate glass, and aluminosilicate glass having a low alkali content. Compositions that do not contain alkali are also preferred. It is preferable that such a glass is manufactured by the above-mentioned down-draw method, overflow down-draw method, or float method, for example.

The carrier substrate preferably has a thickness of at least 100 μm or more, preferably 300 μm or more, more preferably 500 μm or more, and has a thickness of at least 3 inches (1 inch is 2.54 cm) or more, preferably 6 inches or more, more It preferably has a maximum dimension of 8 inches or more, particularly preferably 12 inches or more. In particular, the carrier substrate may have a glass substrate size of the first generation or larger, for example, the second to eighth generations, or a larger substrate size, for example, 1 × 1 m to 3 × 3 m. The carrier substrate may have various shapes, such as rectangular, quadratic or elliptical, or circular.

After the glass substrate is peeled from the carrier substrate together with the contact film by the adhesive force of the contact film, the contact film is peeled off to obtain a glass substrate 22 single body serving as the transparent substrate 3 shown in FIG. 1 .

In a preferred embodiment, it is preferable to reduce the adhesive force between the contact film and the ultrathin substrate by subjecting the contact film to an adhesive weakening treatment before removing the contact film from the glass substrate. The weakening treatment is preferably selected so as to lower the adhesive force to 0.5 N/25 mm or less.

The embrittlement treatment may be selected to be in a specific wavelength range of selected electromagnetic radiation, for example infrared or ultraviolet or visible light. Depending on the adhesive material used, the selected electron radiation may be narrowband, may cover a wider band, or may be laser radiation.

Preferably, it is selected outside the visible spectrum so that the adhesive strength does not deteriorate under exposure to visible light. There are several commercially available adhesive materials that can be at least partially deactivated by irradiation with the electrons, and the preferred choice depends on specific requirements.

Alternatively, when the adhesiveness of the contact film can be reduced by raising or lowering the temperature, it may also be advantageous to perform heat treatment as the embrittlement treatment.

The electron irradiation is preferably applied from the outside of the contact film, that is, from the side not adhered to the glass substrate.

Preferred adhesive materials are widely available and are commercially available, for example, under the trade name of "NDS4150-20", and the corresponding weakening treatment includes ultraviolet irradiation at a wavelength of 365 nm.

Manufacturing examples of specific glass substrates are described in the section of Examples. Moreover, as the glass base material described above, thin glass manufactured by SCHOTT, manufactured by Nippon Electric Glass, etc. can be used.

[2.2] Thermoplastic resin substrate

A thermoplastic resin film can be used for the transparent substrate according to the present invention, and the cut plastic resin is not particularly limited, and cellulose ester-based resins, cycloolefin-based resins, fumaric acid diester-based resins, polypropylene-based resins, ( meth)acrylic resins, polyester-based resins, polyarylate-based resins, polyimide-based resins, and styrene-based resins or composite resins thereof. Especially, it is preferable from a viewpoint of an optical characteristic and a physical characteristic to use the thermoplastic resin film using a polyimide-type resin as the transparent base material 3 shown in FIG.

<Polyimide-based resin>

Polyimide-type resin is obtained, for example, by synthesize|combining a polyamic acid (polyimide precursor) from an acid anhydride and a diamine compound, and imidating the said polyamic acid with a heat|fever or a catalyst.

The acid anhydride used in the synthesis of the polyimide is not particularly limited, but examples thereof include biphenyltetracarboxylic dianhydride (BPDA), terphenyltetracarboxylic dianhydride, and benzophenonetetracarboxylic dianhydride. , aromatic tetracarboxylic acids such as pyromellitic anhydride (PMDA), oxydiphthalic dianhydride, diphenylsulfonetetracarboxylic dianhydride, hexafluoroisopropylidenediphthalic dianhydride, and cyclobutanetetracarboxylic dianhydride. Acid dianhydride etc. are mentioned.

In addition, the diamine compound used in the synthesis of polyimide is not particularly limited, but examples thereof include p-phenylenediamine (PDA), m-phenylenediamine, 2,4-diaminotoluene, and 4,4'. -Diaminodiphenylmethane, 4,4'-diaminodiphenyl ether (ODA), 3,4'-diaminodiphenyl ether, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2 ,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,7-diamino-dimethyldibenzothiophene-5,5'-dioxide, 4,4'-diaminobenzo Aromatic diamines, such as phenone, 4,4'-bis (4-aminophenyl) sulfide, 4,4'- diaminobenzanilide, and 1, 4-bis (4-aminophenoxy) benzene, etc. are mentioned.

Moreover, as a commercial item, the polyimide varnish which has a polyimide precursor as a main component, for example, U-varnish S (made by Ube Kosan Co., Ltd.), Ekrios (made by Mitsui Chemicals Co., Ltd.), etc. can be used.

In the case of using an ultraviolet-transmitting polyimide depending on the purpose, for example, as a polyimide containing a commercially available polyimide precursor (polyamic acid) as a main component, TORMED-S, X (manufactured by IST), Spixeria HR003 , GR003 (above, manufactured by Somar), FLUPI (manufactured by NTT), Type HM (manufactured by Toyobo), Type-C (manufactured by Mitsui Chemicals), PI-100 (manufactured by Maruzen Chemicals), HDN-20D (new Nippon Ewha Co., Ltd.), CBDA-6FDAC (manufactured by Central Glass Co., Ltd.), Q-VR-X-1655 (manufactured by PI Engineering Co., Ltd.), etc. can also be used.

[3] Manufacturing method of cover member

[3.1] Configuration example of cover member

The base film (substrate film 1) of the present invention is disposed on at least one surface of the transparent substrate in the configuration shown in FIG. 1A. As will be described later, when the display device is a display unit having a polarizing plate, it is a preferable embodiment that the base film 1 side of the cover member of the present invention is bonded on the polarizing plate through an adhesive layer.

In the arrangement of the base film on the transparent substrate, on the back side (B side) relative to one side (A side) of the base film, the B side with respect to the film density (ρ _A ) of the A side It is preferable to make the surface A side of the base film adjusted so that the value of the ratio (ρ _A /ρ _B ) of film density (ρ _B ) is in the range of 0.80-0.95 as the transparent substrate side.

It is preferable that the base film 2 mentioned later is arrange|positioned on the surface opposite to the base film 1 of a transparent base material (FIG. 1B).

The base film 1 or the base film 2 is bonded to the transparent base material 3 with an adhesive layer or an adhesive layer.

5 : is a schematic diagram which shows bonding of the base film with a support body and a transparent base material.

5A shows a laminate with the base film 1 formed on the support 5 described above, and the side of the base film 1 in contact with the support 5 corresponds to the B side.

Then, like FIG. 5B, the surface A side of the base film 1 is bonded to the transparent base material 3 via the pressure-sensitive adhesive layer 4, and then the support body 5 is peeled off.

[3.2] Adhesive layer

The pressure-sensitive adhesive layer is preferably obtained by drying and partially crosslinking a pressure-sensitive adhesive composition containing a base polymer, a prepolymer and/or a crosslinkable monomer, a crosslinking agent, and a solvent. That is, at least a part of the pressure-sensitive adhesive composition may be crosslinked.

Examples of the pressure-sensitive adhesive composition include an acrylic pressure-sensitive adhesive composition containing a (meth)acrylic polymer as a base polymer, a silicone pressure-sensitive adhesive composition containing a silicone polymer as a base polymer, and a rubber-type pressure-sensitive adhesive composition containing rubber as a base polymer. Especially, from the viewpoint of transparency, weather resistance, heat resistance, and workability, an acrylic pressure-sensitive adhesive composition is preferable.

The (meth)acrylic polymer contained in the acrylic pressure-sensitive adhesive composition may be a copolymer of a (meth)acrylic acid alkyl ester and a crosslinking agent and a crosslinkable functional group-containing monomer.

It is preferable that (meth)acrylic-acid alkylester is C2-C14 acrylic acid alkylester of an alkyl group.

Examples of the functional group-containing monomer crosslinkable with the crosslinking agent include amide group-containing monomers, carboxyl group-containing monomers (such as acrylic acid), and hydroxyl group-containing monomers (such as hydroxyethyl acrylate).

Examples of the crosslinking agent contained in the acrylic pressure-sensitive adhesive composition include an epoxy-based crosslinking agent, an isocyanate-based crosslinking agent, and a peroxide-based crosslinking agent. The content of the crosslinking agent in the pressure-sensitive adhesive composition may be, for example, 0.01 to 10 parts by mass, for example, based on 100 parts by mass of the base polymer (solid content).

If necessary, the pressure-sensitive adhesive composition may further contain various additives such as tackifiers, plasticizers, glass fibers, glass beads, metal powders, other fillers, pigments, colorants, fillers, antioxidants, ultraviolet absorbers, and silane coupling agents. do.

The thickness of the pressure-sensitive adhesive layer is usually about 3 to 100 μm, and preferably in the range of 5 to 50 μm.

The surface of the pressure-sensitive adhesive layer is protected with a release film subjected to release treatment. Plastic films, such as an acrylic film, a polycarbonate film, a polyester film, and a fluororesin film, are contained in the example of a peeling film.

[3.3] Adhesive layer

Instead of the pressure-sensitive adhesive layer, an adhesive layer may be used, and the pressure-sensitive adhesive layer 4 shown in FIG. 1 may be an adhesive layer.

The adhesive layer is respectively disposed between the base film and the transparent base material. It is also preferable to configure a display device by being disposed between a polarizing plate described later. The type of adhesive contained in the adhesive layer may be the same or different.

The adhesive layer may be a layer obtained from a water-soluble polymer or a layer of a cured product of an active energy ray-curable adhesive. In the case of a water-soluble polymer, for example, an adhesive composed of a vinyl alcohol-based polymer or an adhesive composed of at least a water-soluble cross-linking agent of a vinyl alcohol-based polymer such as boric acid, borax, glutaraldehyde, melamine, or oxalic acid can be used. Such an adhesive layer is formed as a coating and drying layer of an aqueous solution or the like. However, when preparing the aqueous solution, other additives and catalysts such as acids may be incorporated as needed.

The active energy ray-curable adhesive may be a radically photopolymerizable composition or a photocationically polymerizable composition. Especially, a photocationically polymerizable composition is preferable.

A photocationic polymerization composition contains an epoxy-type compound and a photocationic polymerization initiator.

An epoxy-based compound is a compound having one or more, preferably two or more epoxy groups in a molecule. Examples of the epoxy-based compound include hydrogenated epoxy-based compounds obtained by reacting epichlorohydrin with an alicyclic polyol (glycidyl ether of a polyol having an alicyclic ring); Aliphatic epoxy type compounds, such as polyglycidyl ether of an aliphatic polyhydric alcohol or its alkylene oxide adduct; An alicyclic epoxy-based compound having one or more epoxy groups bonded to an alicyclic ring in a molecule is included. An epoxy-type compound may use only 1 type, and may use 2 or more types together.

The photocationic polymerization initiator is, for example, an aromatic diazonium salt; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-arene complexes and the like.

Photocationic polymerization initiators, if necessary, cationic polymerization accelerators such as oxetane and polyol, photosensitizers, ion trapping agents, antioxidants, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow regulators, plasticizers, antifoaming agents , antistatic agent, leveling agent, you may further include additives such as solvents.

The thickness of the adhesive layer is not particularly limited, but is preferably in the range of 0.01 to 10 μm, more preferably in the range of 0.01 to 5 μm.

[3.4] Base film (2)

As the opposite film of the base film 1, the base film 1 may be used, but other resin films may be used. Examples thereof include cycloolefin resins, polypropylene resins, acrylic resins, and polyester resins. , polyarylate-based resins, cellulose ester-based resins, and styrene-based resins or composite resins thereof. Among them, it is preferable to use a resin film containing a polyester-based resin as a resin having excellent storage properties in a high-humidity environment.

Examples of the resin film include polyester-based resins (eg, polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutyl lennaphthalate (PBN), etc.) and the like. Among them, a polyester-based resin film containing polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) is preferable from the viewpoint of ease of handling.

The resin film may be heat treated (heat relaxed) or stretched.

The heat treatment is for reducing the residual stress of the resin film (for example, residual stress accompanying stretching), and is not particularly limited. When the glass transition temperature of the resin constituting the resin film is Tg, (Tg + 60) to (Tg + 180) °C.

The stretching treatment is for increasing the residual stress of the resin film, and it is preferable to perform the stretching treatment in the biaxial direction of the resin film, for example. The stretching treatment can be performed under arbitrary conditions, and can be performed at, for example, a stretching ratio of about 120 to 900%. Whether or not the resin film is stretched can be confirmed, for example, by whether or not there is an in-plane stratum axis (an axis extending in a direction in which the refractive index is maximized). The stretching treatment may be performed before or after lamination of the base film, but it is preferable that the stretching is performed before lamination.

A commercial product can be used for the polyester-based resin film (simply referred to as a polyester film), for example, polyethylene terephthalate film TN100 (manufactured by Toyobo Co., Ltd.), MELINEX ST504 (manufactured by Teijin Dupont Film Co.), etc. can be preferably used.

Although the film thickness of the base film 2 can be taken suitably, it is preferable that it exists in the range of 10-100 micrometers from a viewpoint of thinning of a cover member, and it is more preferable that it exists in the range of 10-50 micrometers.

Moreover, you may provide functional layers, such as a hard-coat layer, to the base film 2.

(hard coat layer)

The polyester film placed on the surface of the foldable display to protect the display preferably has a hard coat layer on the surface. It is preferable that the hard coat layer is placed on the display surface side on the polyester film and used in the display. As the resin forming the hard coat layer, an acrylic type, a siloxane type, an inorganic hybrid type, a urethane acrylate type, a polyester acrylate type, an epoxy type, etc. can be used without particular limitation. Moreover, two or more types of materials may be mixed and used, and particles such as inorganic fillers and organic fillers may be added.

As a film thickness of a hard-coat layer, the range of 1-50 micrometers is preferable. When it is 1 micrometer or more, it hardens sufficiently and favorable pencil hardness is obtained. In addition, by setting the thickness to 50 μm or less, curl due to curing shrinkage of the hard coat can be suppressed, and handling properties of the film can be improved.

As the coating method of the hard coat layer, wire bar, gravure coat, die coater, knife coater, etc. can be used without particular limitation, and can be appropriately selected depending on the viscosity and film thickness.

As a method of curing the hard coat layer, energy rays such as ultraviolet rays or electron beams, or a method of curing by heat can be used. In order to reduce damage to the film, a method of curing by ultraviolet rays or electron beams is preferable.

As a pencil hardness of a hard-coat layer, B or more is preferable, H or more is more preferable, and 2H or more is especially preferable. When there is a pencil hardness of B or more, scratches do not easily occur and visibility is not reduced. In general, the hard coat layer preferably has a higher pencil hardness, but it may be 9H or less, 8H or less, and 6H or less can be used without any problem in practical use.

The hard coat layer used in the present invention can be used for the purpose of protecting the display by increasing the pencil hardness of the surface as described above, and preferably has a high transmittance. As transmittance of a hard coat film, 87 % or more is preferable and 88 % or more is more preferable. When the transmittance is 87% or more, sufficient visibility is obtained. The total light transmittance of the hard coat film is generally so preferable that it is higher, but may be 99% or less, and may be 97% or less. Moreover, as for the haze of a hard coat film, it is preferable that it is generally low, and 3 % or less is preferable. The haze of the hard coat film is more preferably 2% or less, and most preferably 1% or less. When the haze is 3% or less, the visibility of the image can be improved.

The hard coat layer may also have other functions added to it. For example, a hard coat layer having added functionality such as an anti-glare layer having a certain pencil hardness, an anti-glare antireflection layer, an antireflection layer, a low reflection layer, and an antistatic layer as described above is also preferably applied in the present invention.

[4] Display device

The display device of the present invention is characterized by comprising the cover member or the base film for the cover member of the present invention. The display device of the present invention can be obtained by, for example, bonding the cover member of the present invention to the surface of the display device through an adhesive agent layer or an adhesive layer, preferably through a polarizing plate. A display device is a device having a display mechanism, and includes a light emitting element or a light emitting device as a light emitting source. As the display device, a liquid crystal display device, an organic electroluminescence (EL) display device, an inorganic electroluminescence (EL) display device, a touch panel display device, an electron emission display device (electric field emission display device (FED, etc.), surface field emission display (SED)), electronic paper (display device using electronic ink or electrophoretic element), plasma display device, projection type display device (grating light valve (GLV) display device, digital micro mirror device (DMD)) a display device having the same), a piezoelectric ceramic display, and the like. The liquid crystal display device includes any one of a transmission type liquid crystal display device, a transflective type liquid crystal display device, a reflection type liquid crystal display device, a direct view type liquid crystal display device, and a projection type liquid crystal display device. These display devices may be display devices that display two-dimensional images or stereoscopic display devices that display three-dimensional images. In particular, as the display device of the present invention, an organic EL display device and a touch panel display device are preferable, and an organic EL display device is particularly preferable.

Further, it is preferable that the foldable display has a structure in which a continuous display can be folded in two when carrying, thereby reducing the size by half and improving portability. Moreover, it is preferable to be thin and lightweight at the same time. Therefore, the bending radius of the foldable display is preferably 5 mm or less, more preferably 3 mm or less. If the bending radius is 5 mm or less, thinning in a folded state becomes possible. Although it can be said that a bending radius is so good that it is small, it does not matter if it is 0.1 mm or more, and it does not matter even if it is 0.5 mm or more. Even if it is 1 mm or more, the practicality is sufficiently good compared to the conventional display without a folding structure. Here, the bending radius when folded means the inner radius R of the folded portion when the cover member 10 is folded in the above-described FIG. 1C or FIG. 1D.

6 shows an example of application of the cover member to an organic EL display, which is an example of the display device of the present invention.

A general configuration of an organic EL display is an organic EL layer 101 composed of an electrode/electron transport layer/light emitting layer/hole transport layer/transparent electrode, and a polarizing plate 102 provided with a retardation plate (λ/4 plate) for improving image quality. It is a display unit consisting of In the display device 100 of the present invention, it is a preferable embodiment that the base film 1 side of the cover member 10 of the present invention is bonded together on the polarizing plate 102 with the pressure-sensitive adhesive layer 4 interposed therebetween.

According to this embodiment, the display device of the present invention is a display device in which, in addition to improving the handleability of the cover member, creases do not occur on the base film with which the cover member is provided, particularly as a cover member for a foldable display, for mass production. It is excellent in visibility after repeated folding while maintaining stability, and does not cause disorder of the image in the folded part of the display. For example, a portable terminal device equipped with the foldable display provides a beautiful image, is rich in functionality, and has excellent convenience such as portability.

Example

Hereinafter, the present invention will be described in detail with examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise specified, "part by mass" or "mass %" is shown.

<<Manufacture of base film>>

<Manufacture of base film 101>

(support)

As the support, a polyethylene terephthalate film (PET film): (TN100 manufactured by Toyobo, a release layer containing a non-silicone-based release agent, a film thickness of 38 µm) was used.

(Preparation of solution for base film 101)

The following components were mixed to obtain a solution for base film 101.

Methylene chloride (boiling point 41 ℃) 800 parts by mass

Acrylic 1: MMA/PMI/MADA copolymer (60/20/20 mass ratio), Mw: 1.5 million, Tg: 137° C. (In addition, the abbreviation indicates the following. MMA: methyl methacrylate, PMI: phenylmaleimide, and MADA: adamantyl acrylate) 20 mass parts

Rubber particle R1: 80 parts by mass

Dispersant (sodium polyoxyethylene lauryl ether phosphate: molecular weight: 332) added in an amount of 0.006% by mass in the base film

(Manufacture of base film 101)

On the release layer of the support, the solution for the base film 101 was applied using a die by the back coating method, and then the base film was dried in the following drying step to form a base film having a thickness of 5 μm. , to obtain a base film 101.

(initial drying)

1st step: 1 minute at 40 °C

2nd step: 1 minute at 70 °C

3rd step: 1 minute at 100 °C

4th step: 2 minutes at 130 ℃

(Post-drying)

5th step: 15 minutes at 110°C

<Preparation of rubber particle R1>

Rubber particles prepared by the following method were used.

In an 8 L polymerization apparatus equipped with an agitator, the following substances were charged.

deionized water 180 parts by mass

Polyoxyethylene lauryl ether phosphoric acid 0.002 parts by mass

boric acid 0.473 parts by mass

sodium carbonate 0.473 parts by mass

sodium hydroxide 0.008 parts by mass

After sufficiently substituting the inside of the polymerization reactor with nitrogen gas, the internal temperature was set to 80°C, and 0.021 parts by mass of potassium persulfate was introduced as a 2% by mass aqueous solution. Next, 21 parts by mass of a monomer mixture (c′) consisting of 84.6% by mass of methyl methacrylate, 5.9% by mass of butyl acrylate, 7.9% by mass of styrene, 0.5% by mass of allyl methacrylate, and 1.1% by mass of n-octylmercaptan was added to poly A liquid mixture in which 0.07 parts by mass of oxyethylene lauryl ether phosphoric acid was added was continuously added to the solution over 63 minutes. Further, the innermost hard polymer (c) was obtained by continuing the polymerization reaction for 60 minutes.

Then, 0.021 mass part of sodium hydroxide was made into 2 mass % aqueous solution, and 0.062 mass part of potassium persulfate was added as a 2 mass % aqueous solution, respectively. Subsequently, a liquid mixture obtained by adding 0.25 parts by mass of polyoxyethylene lauryl ether phosphoric acid to 39 parts by mass of the monomer mixture (a') consisting of 80.0% by mass of butyl acrylate, 18.5% by mass of styrene, and 1.5% by mass of allyl methacrylate was added over 117 minutes. added successively. After completion of the addition, 0.012 parts by mass of potassium persulfate was added as a 2% by mass aqueous solution, and the polymerization reaction was continued for 120 minutes to obtain a soft layer (a layer made of acrylic rubber-like polymer (a)). The glass transition temperature (Tg) of the soft layer was -30°C. The glass transition temperature of the soft layer was calculated by averaging the glass transition temperatures of homopolymers of each monomer constituting the acrylic rubber-like polymer (a) according to the composition ratio.

Thereafter, 0.04 parts by mass of potassium persulfate was added in a 2% by mass aqueous solution, and 26.1 parts by mass of a monomer mixture (b') composed of 97.5% by mass of methyl methacrylate and 2.5% by mass of butyl acrylate was added continuously over 78 minutes. Further, the polymerization reaction was continued for 30 minutes to obtain a polymer (b).

The obtained polymer (b) was put into a 3% by mass sodium sulfate warm water solution, and salted out and coagulated. Then, after repeating dehydration and washing, drying was performed to obtain acrylic graft copolymer particles having a three-layer structure (rubber particle R1). The average particle diameter of the obtained rubber particle R1 was 200 nm.

The average particle diameter of rubber particles was measured by the following method.

(average particle size)

The dispersion particle size of the rubber particles in the obtained dispersion was measured with a zeta potential/particle size measurement system (ELSZ-2000ZS manufactured by Otsuka Electronics Co., Ltd.).

<Manufacture of base films 102 to 104>

In manufacture of the base film 101, the base films 102-104 were manufactured similarly except having changed content of rubber particle R1 to 65, 45, and 20 mass %, respectively.

<Manufacture of base film 105>

(support)

As the support, a polyethylene terephthalate film (PET film): (TN100 manufactured by Toyobo, a release layer containing a non-silicone-based release agent, a film thickness of 38 µm) was used.

(Preparation of solution for base film 105)

The following components were mixed to obtain a solution for base film 105.

Methylene chloride (boiling point 41 ℃): 860 mass parts

Methanol (boiling point 65 ℃): 40 parts by mass

COP1 (G7810: ARTON G7810 manufactured by JSR Co., Ltd., Mw: 140,000, cycloolefinic resin having a carboxylic acid group) 100 parts by mass

Antioxidant (Irganox 1076: manufactured by BASF: molecular weight 531)

In the base film, an addition amount of 0.002% by mass is added.

(Manufacture of base film 105)

On the release layer of the support, the solution for base film 105 was applied using a die by the back coating method, and then the base film was dried in the following drying step to form a base film having a thickness of 5 μm. , to obtain a base film 105.

1st step: 1 minute at 40 °C

2nd step: 1 minute at 70 °C

3rd step: 1 minute at 100 °C

4th step: 2 minutes at 130 ℃

<Manufacture of base film 106>

(support)

As the support, a polyethylene terephthalate film (PET film): (TN100 manufactured by Toyobo, a release layer containing a non-silicone-based release agent, a film thickness of 38 µm) was used.

(Preparation of polyimide powder)

5.146 g (20 mmol) of MeO-DABA represented by the following formula was placed in a four-necked flask equipped with a dry nitrogen gas inlet tube, a condenser, a Dean-Stark condenser filled with toluene, and a stirrer, and γ-butyrolactone (GBL) 20 mL and 10 mL of toluene were added, and the mixture was stirred at room temperature under a nitrogen stream.

[Formula 6]

To it, 4.483 g (20 mmol) of cis,cis,cis-1,2,4,5-cyclohexanetetracarboxylic dianhydride (H-PMDA) powder was added, and the mixture was heated and stirred at 80°C for 6 hours. Then, the external temperature was heated to 190 degreeC, and the water generated with imidation was removed by azeotropic distillation together with toluene. As a result of continuing heating, refluxing and stirring for 6 hours, generation of water was not observed. It heated for 7 hours, distilling off toluene then, and also reprecipitated by throwing in methanol after toluene distillation, and obtained 6.4 g of polyimide powder (yield 72%).

(Preparation of solution for base film 106)

The following components were mixed to obtain a solution for the base film 106.

Methylene chloride (boiling point 41 ℃) 900 parts by mass

Polyimide 1 (the above polyimide powder) 100 parts by mass

(Manufacture of base film 106)

After applying the solution for the base film 106 on the release layer of the support body using a die by the back coating method, the base film was dried in the following drying step to obtain a base film 106 having a film thickness of 5 μm. .

(initial drying)

1st step: 1 minute at 40 °C

2nd step: 1 minute at 70 °C

3rd step: 1 minute at 100 °C

4th step: 2 minutes at 130 ℃

(Post-drying)

5th step: 15 minutes at 110°C

<Manufacture of base films 107 and 108>

In the production of the base film 101, the base films 107 and 108 were manufactured in the same manner except that the film thickness was changed to 10 μm and 14 μm, respectively.

<Manufacture of base film 109>

In manufacture of the base film 105, the base film 109 was similarly manufactured except having adjusted the solid content concentration of COP1 (G7810) in dope to be 20 mass %.

<Manufacture of base film 110>

In manufacture of the base film 105, the base film 110 was similarly manufactured except having used the following dope which added silica fine particles in dope.

(Preparation of microparticle addition liquid)

Silica fine particles (Aerosil R812: manufactured by Nippon Aerosil Co., Ltd., primary average particle diameter: 7 nm, apparent specific gravity 50 g/L) 4 parts by mass

dichloromethane 48 mass parts

ethanol 48 mass parts

After stirring and mixing the above for 50 minutes with a dissolver, dispersion was performed with Manton Goolin. In addition, dispersion was performed with an attritor so that the particle size of the secondary particles became a predetermined size. This was filtered through Fine Met NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive liquid.

(Preparation of solution for base film 110)

A dope having the following composition was prepared. First, dichloromethane and ethanol were added to a pressurized dissolution tank. Cycloolefin-based resin (DOP): G7810 was added while stirring to a pressurized dissolution tank containing a mixed solution of dichloromethane and ethanol. Further, 15 minutes after the start of the solvent injection, the microparticles additive liquid prepared above was introduced, and it was completely dissolved while heating and stirring this at 80°C. At this time, the temperature was raised from room temperature at 5°C/min, dissolved for 30 minutes, and then cooled at 3°C/min. The obtained solution was filtered using Azumi Filter Paper Co., Ltd. product Azumi Filter Paper No. 244 to prepare dope.

(Composition of dope)

COP1 (G7810) 100 parts by mass

dichloromethane 200 parts by mass

ethanol 10 parts by mass

particulate addition solution 1 part by mass

<Manufacture of base film 111>

In the manufacture of the base film 102, the base film 111 was manufactured in the same manner as in the manufacturing process, except that the PET film serving as the support was peeled off, the B side was dried, and then the PET film was again pasted on the B side and wound up.

<Manufacture of base film 112>

In manufacture of the base film 105, the base film 112 was similarly manufactured except having added rubber particle R1 so that it might become 65 mass % in dope.

<Manufacture of base film 113>

(support)

As a support, Kapton Film 200 H/V (made by Toray DuPont, 50 µm in thickness) was used.

(Manufacture of base film 113)

2,2'-ditrifluoromethyl-4,4'-diamino corresponding to 90 mol% of the total amount of diamine as diamine in dehydrated dimethylacetamide (DMAc, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 165 ° C.) Biphenyl (TFMB, manufactured by Toray Fine Chemical Co., Ltd.) and 4,4'-diaminodiphenyl ether (DPE, manufactured by Tokyo Chemical Industry Co., Ltd.) corresponding to 10 mol% were dissolved under a nitrogen stream, and the liquid temperature was cooled to 5 in an ice water bath. cooled to °C. Thereto, 2-chloroterephthaloyl chloride (CTPC, manufactured by Nippon Light Metal Co., Ltd.) corresponding to 99 mol% relative to the total amount of diamine was added over 30 minutes in a state where the inside of the system was maintained in an ice water bath under a nitrogen stream. After adding the entire amount, stirring was performed for about 2 hours to polymerize the aromatic polyamide (polymer A). To the obtained solution, as a neutralizing agent, allylglycidyl ether (Tokyo Chemical Industry Co., Ltd., neutralizing agent E) corresponding to 100 mol% relative to the amount of hydrogen chloride generated by the reaction (ie, the amount of amide groups of the aromatic polyamide) was added, and about 1 An aromatic polyamide solution composed of polymer A (polyamide 1) was obtained by stirring for an hour.

The obtained aromatic polyamide solution was cast in the form of a film on the support at room temperature using an applicator, and dried in a hot air oven at 115 ° C. for 30 minutes and 265 ° C. for 5 minutes to obtain polymer A with a film thickness of 5 μm (poly A base film 113 made of amide 1) was obtained. Here, the hot air oven was used using Safety Oven SPH100 (manufactured by ESPEC Corporation) 1 hour after the temperature display reached the set temperature with an opening/closing damper of 50%.

<Manufacture of base film 114>

(support)

As a support, Kapton Film 200 H/V (made by Toray DuPont, 50 µm in thickness) was used.

(Manufacture of base film 114)

9,9-bis(4-aminophenyl)fluoride as a diamine component in a 300 mL five-necked round bottom flask equipped with a stainless steel half-moon shaped stirring blade, a nitrogen inlet tube, a Dean Stark equipped with a cooling tube, a thermometer, and a glass end cap. Orene (manufactured by Taoka Chemical Industry Co., Ltd.) 9.76 g (0.028 mol) and 2,2-bis [4- (4-aminophenoxy) phenyl] propane (manufactured by Wakayama Purification Industry Co., Ltd.) 8.62 g (0.021 mole), 4, 6.72 g (0.021 mol) of 4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (manufactured by Wakayama Seiki Kogyo Co., Ltd.) and 46.86 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) were added, , The solution was obtained by stirring at a rotational speed of 200 rpm under a nitrogen atmosphere at a system internal temperature of 70°C.

To this solution, 16.47 g (0.07 mol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (manufactured by Mitsubishi Gas Chemical Co., Ltd.) and γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) were added as tetracarboxylic acid components. ) 11.72 g was added at once, and then 3.54 g of triethylamine (manufactured by Kanto Chemical Co., Ltd.) was added as an imidation catalyst, heated with a mantle heater, and the temperature in the reaction system was raised to 190 ° C. over about 20 minutes. Components to be distilled off were collected and refluxed for 5 hours while maintaining the internal temperature of the reaction system at 190°C while adjusting the number of revolutions according to the increase in viscosity.

After that, 97.62 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) was added, the temperature inside the reaction system was cooled to 120°C, and then stirred for about 3 hours to homogenize, and polyimide 2 having a solid content concentration of 20% by mass got a solution. Subsequently, on the support, the obtained polyimide 2 solution is applied using a die by the back coating method in the same manner as in the production of the base film 101, and then the base film is dried in the following drying step to increase the film thickness. A base film of 5 µm was formed to obtain a base film 114.

(initial drying)

1st step: 10 minutes at 40 °C

2nd step: 10 minutes at 70 °C

3rd step: 30 minutes at 100 °C

4th step: 30 minutes at 130 ° C

(Post-drying)

5th step: 30 minutes at 250°C

<Manufacture of base film 115>

(support)

As the support, a polyethylene terephthalate film (PET film): (TN100 manufactured by Toyobo, a release layer containing a non-silicone-based release agent, a film thickness of 38 µm) was used.

(Preparation of solution for base film 115)

Methyl Ethyl Ketone (MEK) 90 parts by mass

rubber particle R1 10 parts by mass

A solution for base film 115 was obtained by stirring with a magnetic stirrer.

(Manufacture of base film 115)

On the release layer of the support, the solution for base film 115 was applied using a die by the back coating method, and then the base film was dried in the following drying step to form a base film having a thickness of 5 μm. , to obtain a base film 115.

(initial drying)

1st step: 1 minute at 40 °C

2nd step: 1 minute at 70 °C

3rd step: 1 minute at 100 °C

4th step: 2 minutes at 130 ℃

(Post-drying)

5th step: 15 minutes at 110°C

<Manufacture of base film 116>

In manufacture of the base film 102, the base film 116 was manufactured similarly except having adjusted the film thickness to 25 micrometers.

≪Evaluation≫

The following evaluation was performed using the obtained base film.

<Stress-strain curve>

The base film was cut out to a size of 100 mm (MD direction: longitudinal direction) x 10 mm (TD direction: transverse direction) to obtain a sample film. This sample film was subjected to humidity control for 24 hours in an environment of 23 ° C. and 55% RH, and the sample film after humidity control was subjected to JIS K7127: 1999 using Tensilon RTC-1225A manufactured by Orientec Co., Ltd., and the distance between chucks was 50 mm, and a stress-strain curve until fracture was obtained while stretching in the MD direction. In the stress-strain curve, the vertical axis represents stress (MPa), and the horizontal axis represents tensile elongation at break (%). The stress-strain curve was measured under conditions of 23°C/55% RH and a tensile speed of 50 mm/min.

From the stress-strain curve of the base film obtained by the above measurement, the slope of the straight line related to the present invention was determined.

As shown in Fig. 2, the base film is subjected to a tensile test to take a breaking point X after stretching. When a weave Y connecting the breaking point X and the origin (0 point) is drawn, the slope α of this straight line is , "the inclination of the straight line connecting the origin and the breaking point in the stress-strain curve of the base film" as used in the present invention.

<Measurement of Density of Surface A and Surface B of Base Film>

The density of the surface (A side and B side) of the base film was measured using the X-ray reflectance method (XRR method). X-rays are totally reflected when they are incident on the film surface at a very shallow angle, and when the angle of the incident X-rays is greater than the critical angle of total reflection, the X-rays penetrate the inside of the film and the reflectance is lowered. The reflectance profile measured by the XRR method can be analyzed using dedicated reflectance analysis software. In the present invention, when θa is the angle at which the reflectance starts to decrease, 2θ is in the range of 2θa to 2θa + 0.1°. , the density at which the fitting error between the measurement result and the calculation result was the smallest was set as the surface density. At that time, the surface roughness was set within the range of 0 to 1 nm, and fitting was performed.

The base film was cut out to a size of 30 mm x 30 mm, fixed to a sample stage, and measured under the following measurement conditions.

(Measuring conditions)

·Device : Thin-film X-ray diffractometer (ATX-G manufactured by Rigaku Co., Ltd.)

・Sample size : 30 mm × 30 mm

･Incident X-ray wavelength : 1.5405 Å

・Measurement range (θ) : 0 to 6°

・Analysis software: Reflectance analysis software GXRR (manufactured by Rigaku Co., Ltd.)

<Measurement of elastic modulus of base film>

The measurement conditions for the elastic modulus (also referred to as tensile elastic modulus) were set as follows, and the elastic modulus was determined by linear regression between strains of 0.05 and 0.25%.

About the MD direction, based on JIS K7127 (1999), the tensile modulus was measured by the following method.

1) The base film was cut out to a size of 100 mm (MD direction) x 10 mm (TD direction) to obtain a test piece.

2) This test piece was stretched at a tensile rate of 50 mm/min in the longitudinal direction (MD direction) of the test piece at a distance between chucks of 50 mm using Tensilon RTC-1225A manufactured by Orientec, and the tensile elastic modulus in the MD direction was measured. The measurement was performed at 23°C and 55% RH. In addition, the elastic modulus of the transparent substrate described later was also measured in the same manner.

<Indentation strength>

About side A and side B of a base film, it measured according to the procedure of the indentation test stipulated by ISO14577. Under an environment of 23 ° C. and 55% RH, an ultra-micro hardness tester (manufactured by Fisher Instruments, trade name “Fisher Scope 100C”) was used as a tester, and as an indenter, a pyramidal diamond indenter having a square base and a face angle of 136° was used. The measurement was carried out using

For the measurement, a load of 10 mN was applied by pressing an indenter into the base film at a constant speed. The calculation of the Martens hardness was obtained by applying a load (10 mN) to the film and dividing it by the surface area of the indenter penetrating beyond the contact zero point.

Regarding the indentation strength of the base film of the present invention, the Martens hardness was measured according to the above method, and the surface hardness (Martens hardness) rank was determined for the average value of the A side and the B side according to the following criteria. .

◎: Martens hardness of 200 N/㎟ or more

○: Martens hardness of 50 N/mm2 or more and less than 200 N/mm2

△: Martens hardness of 25 N/mm2 or more and less than 50 N/mm2

×: Martens hardness less than 25 N/mm2

If the evaluation rank of the Martens hardness is Δ or more, the indentation strength of the base film is improved, cracking of the transparent base material is prevented when the base film is attached to the cover member, and the handleability of the cover member is improved. Preferably, it is ○ - ◎.

The composition and evaluation results of the base film are shown in Table I below.

<Manufacture of transparent substrate 1: in the table, marked with glass.>

A glass substrate having dimensions of 12 inches was prepared according to the following process (see Fig. 4).

(Step 1) A contact film (also referred to as “contact film”) formed on a glass carrier substrate having a bonding surface so that the first surface of the glass substrate surface is in contact with the second surface on the opposite side to the first surface. ) process of attaching.

(Process 2) Then, the process of peeling a glass base material from a carrier substrate with the contact film with high adhesive force.

(Step 3) A step of removing the contact film from the second surface of the glass substrate separated from the carrier substrate by a weakening treatment (electron radiation irradiation) that weakens the adhesive strength of the contact film.

After forming the glass base material 1 so that it might become predetermined thickness so that it might contact|connect a 500-micrometer-thick carrier substrate by process 1, the following contact film was attached. Subsequently, the carrier substrate was removed by peeling the glass substrate together with the contact film from the carrier substrate for 30 seconds (Step 2). As the contact film, one commercially available under the trade name "NDS4150-20" containing polyolefin (PO) as a substrate having a thickness of 150 µm and an adhesive layer of 10 µm was used.

Subsequently, the exposed contact film was subjected to a weakening treatment to reduce adhesion. For the embrittlement treatment, the contact film was irradiated with a 365 nm ultraviolet ray for 10 seconds. The irradiation power of ultraviolet rays was about 500 mW/cm 2 , and the total irradiation energy was 500 mJ/cm 2 . At that time, the adhesive force before the embrittlement treatment was about 11 N/25 mm, and after the embrittlement treatment, the adhesive force was reduced to 0.4 N/25 mm. Thereby, the contact film could be easily peeled off from the glass substrate, and a glass substrate single body having a thickness of 28 μm was obtained (Step 3).

In addition, the thickness of the transparent substrate was adjusted to 8 μm, 28 μm, 45 μm, and 54 μm, and the elastic modulus by the above-described measurement method was as described in Table II, respectively.

<Manufacture of transparent substrate 2: In the table, indicated as polyimide.>

In the production of the base film 114, the obtained polyimide 2 solution was applied onto a glass plate, maintained at 100°C for 60 minutes on a hot plate, and the solvent was evaporated to obtain a colorless and transparent primary drying film having self-supporting properties. This film was fixed to a stainless steel frame and heated at 250°C for 2 hours in a hot air dryer to evaporate the solvent to obtain a transparent substrate 2 having a thickness of 28 µm. The elastic modulus by the above-mentioned measurement method was 10 GPa.

<Manufacture of base film 2>

(Preparation of polyethylene terephthalate pellets (a))

As an esterification reaction device, a continuous esterification reaction device consisting of a three-stage complete mixing tank having a stirring device, a condenser, a raw material inlet and a product outlet is used, terephthalic acid (TPA) is 2 tons / hr, ethylene glycol (EG) in an amount of 2 mol with respect to 1 mol of TPA, antimony trioxide in an amount of 160 ppm of antimony (Sb) atoms with respect to produced PET, and continuously supplying these slurries to the first esterification reaction can of the esterification reaction unit and reacted at 255°C with an average residence time of 4 hours at normal pressure.

Subsequently, the reaction product in the first esterification reaction can is continuously taken out of the system and supplied to the second esterification reaction can, and EG distilled off from the first esterification reaction can is produced in the second esterification reaction can. EG solution supplied at 8% by mass relative to (produced PET) and containing magnesium acetate in an amount such that the magnesium (Mg) atom is 65 ppm relative to produced PET, and an amount of P atom equal to 20 ppm relative to generated PET An EG solution containing tetramethylphthalic acid (TMPA) was added and reacted at 260°C with an average residence time of 1.5 hours under normal pressure. Then, the reaction product in the second esterification reaction can is continuously taken out of the system and supplied to the third esterification reaction can, and an EG solution containing TMPA in an amount such that the P atom is 20 ppm with respect to the product PET is added. and reacted at 260°C with an average residence time of 0.5 hours at normal pressure. The esterification product produced in the third esterification reaction can is continuously supplied to a three-stage continuous polycondensation reactor to perform polycondensation, and a filter medium of a stainless steel sintered body (nominal filtration accuracy of 5 μm particles 90% cut ) to obtain polyethylene terephthalate pellets (a) having an intrinsic viscosity of 0.580 dl/g.

(Manufacture of polyethylene terephthalate film)

The polyethylene terephthalate pellet (a) was fed into an extruder and melted at 285°C. This polymer is filtered with a stainless steel sintered filter medium (nominal filtration accuracy of 10 μm particles, 95% cut), and after extruding into a sheet form from a nozzle, it is brought into contact with a casting drum with a surface temperature of 30 ° C. using an electrostatic application casting method It was made to solidify by cooling, and the unstretched film was made. This unstretched film was uniformly heated at 75°C using a heating roll and heated at 100°C with a non-contact heater to perform roll stretching (longitudinal stretching) 1.5 times. The obtained uniaxially stretched film is guided to a tenter, heated at 125°C, transversely stretched 5.5 times, fixed in width, subjected to heat treatment at 190°C for 5 seconds, and further relaxed by 4% in the width direction at 100°C. A base film 2, which is a 50 μm polyethylene terephthalate film, was obtained (in the table, it is indicated as PET).

<Manufacture of cover member>

<Manufacture of cover member 201>

The cover member 201 shown in Table II was manufactured by bonding together the base film 101 manufactured in Example 1, the transparent base material 1, and the base film 2 manufactured above through the following pressure-sensitive adhesive layer.

<Material of the pressure-sensitive adhesive layer>

(Preparation of acrylic polymer)

A monomer mixture containing 100 parts of n-butyl acrylate and 5 parts of acrylic acid was charged into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. In addition, with respect to 100 parts of the monomer mixture (solid content), 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator was injected together with 100 parts of ethyl acetate, and nitrogen gas was introduced while stirring slowly to replace nitrogen , A solution of an acrylic polymer having a weight average molecular weight (Mw) of 1,600,000 was prepared by carrying out a polymerization reaction for 8 hours while maintaining the liquid temperature in the flask at around 55°C.

(Preparation of pressure-sensitive adhesive composition solution)

0.45 part of an isocyanate-based crosslinking agent (Colonate L, trimethylolpropantolylene diisocyanate manufactured by Tosoh Corporation) was blended with 100 parts of solid content of the acrylic polymer solution obtained above to prepare a solution of an acrylic pressure-sensitive adhesive composition.

(Formation of pressure-sensitive adhesive layer and manufacture of cover member)

Next, corona discharge treatment was performed on the A side of the base film 101 at a corona output intensity of 2.0 kW and a line speed of 18 m/min, and the prepared adhesive composition solution was applied to the corona discharge treated surface, and the film thickness after drying was about 3 μm. After coating with a bar coater so as to be, it was dried at 50 ° C., 60 ° C., and 70 ° C. in this order for 60 seconds to form an adhesive layer, and then, after bonding, the support of the base film 101 was peeled off to obtain a cover member 201 (Fig. See 5B.).

<Manufacture of cover members 202 to 222>

In the manufacture of the cover member 201, the cover members 202 to 222 were manufactured in the same manner except that the combination of each type of the base film 1, the transparent base material, and the base film 2 was changed as described in Table II.

For the cover member 214, in the production of the cover member 202, the base film 102 prepared above was also used for the base film 2. In addition, bonding of the base film 2 was also bonded so that the side A side of the base film 102 was disposed on the glass substrate side. In the production of the cover member 202, the cover member 215 was not bonded to the base film 2 side.

≪Evaluation≫

<Evaluation of fold marks>

A cover member sample having a size of 20 mm in the TD direction and 110 mm in the MD direction is prepared. It was made to bend 100 times at the speed of 1 time/sec using the unloaded U-shaped extension tester (DLDMLH-FS, manufactured by Yuasa System Equipment Co., Ltd.) by setting the bending radius of 1 mm. At that time, the sample fixed the position of 10 mm of both ends on the MD side, and the bent portion was 20 mm x 90 mm. After the end of the bending process, the sample is placed on a flat surface with the inside of the bend facing down, and the haze value before evaluation is set to A and the haze value after evaluation is set to B with a commercially available haze meter at the bent portion. - A) was obtained and the following rank classification was performed.

◎ : Less than 0.2

○: 0.2 or more and less than 0.5

△: 0.5 or more and less than 1.0

×: 1.1 or more

△ or more is preferable.

The configuration of the cover member and the above evaluation results are shown in Table II below.

From the results of Table I and Table II, the cover members 201 to 217 using the base films 101 to 112 of the present invention are different from the cover members 218 to 221 using the base films 113 to 116 of the comparative example and the cover member 222 in which the transparent base material is a thick film. In comparison, excellent results were obtained in both evaluations of the indentation strength of the base film and the crease of the cover member.

The cover member of the present invention, in addition to improving handleability, has a feature that no creases are formed on the base film attached to the cover member when repeatedly bent, so that the image is not disturbed at the folded portion of the display. , As a display device with a cover member having excellent visibility, it can be suitably used for a foldable display using an organic electroluminescent element.

1: base film 1
2: base film 2
3: transparent substrate
4: adhesive layer
5: support
10: cover member
21: carrier substrate
22: glass substrate
23: contact film
24: electron radiation
100: display device
101 organic EL layer
102: polarizer
B110: support
B120: base film
B200: Manufacturing device
B210: supply section
B220: applicator
B230: drying part
B240: cooling section
B250: winding part
R: bending radius

Claims (10)

A cover member having a substrate film of 1 μm or more and less than 15 μm and a transparent substrate of 5 μm or more and less than 50 μm,
A cover member characterized in that the slope of a straight line connecting the origin and the break point in the stress-strain curve of the base film is 1.1 or more and 25.0 or less. According to claim 1,
When the bonding surface of the base film with the transparent substrate is the A surface and the back surface of the base film relative to the A surface is the B surface,
The cover member characterized in that the film density (ρ _A ) of the surface A is smaller than the film density (ρ _B ) of the surface B. According to claim 1 or 2,
When the bonding surface of the base film with the transparent substrate is the A surface and the back surface of the base film relative to the A surface is the B surface,
A value of a ratio (ρ _A /ρ _B ) of the film density (ρ _B ) of the surface B to the film density (ρ _A ) of the surface A is within a range of 0.80 to 0.95. According to any one of claims 1 to 3,
The cover member characterized in that the base film contains rubber particles within a range of 40 to 85% by mass. According to any one of claims 1 to 4,
The elastic modulus of the transparent substrate is in the range of 55 to 80 GPa, and the value of the elastic modulus of the transparent substrate and the elastic modulus ratio of the base film (elastic modulus of the transparent substrate / elastic modulus of the base film) is 30 or more Cover, characterized in that absence. As a base film for a cover member,
The base film is 1 μm or more and less than 15 μm,
A base film for a cover member, characterized in that the slope of a straight line connecting the origin and the break point in the stress-strain curve of the base film is 1.1 or more and 25.0 or less. According to claim 6,
The base film is bonded to a transparent base material,
When the bonding surface of the base film with the transparent substrate is the A surface and the back surface of the base film relative to the A surface is the B surface,
A base film for a cover member, wherein the film density (ρ _A ) of the surface A is smaller than the film density (ρ _B ) of the surface B. According to claim 6 or 7,
The base film is bonded to a transparent base material,
When the bonding surface of the base film with the transparent substrate is the A surface and the back surface of the base film relative to the A surface is the B surface,
A substrate for a cover member, characterized in that a value of a ratio (ρ _A /ρ _B ) of the film density (ρ _B ) of the surface B to the film density (ρ _A ) of the surface A is within a range of 0.80 to 0.95. film. According to any one of claims 6 to 8,
The base film for a cover member characterized in that the base film contains rubber particles within a range of 40 to 85% by mass. A display device comprising the cover member according to any one of claims 1 to 5 or the base film for a cover member according to any one of claims 6 to 9.

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